feat(eval/method): partially port v8.1.1996

Problem:    More functions can be used as methods.
Solution:   Make various functions usable as a method.
aad222c9c9

Partial port as this does not include eval.txt change for listener_add.

Cherry-pick eval.txt changes for:
- bufadd from v8.1.1626:
  5ca1ac373a
- setloclist and setqflist headers from:
  b0d45e7f53

Correct eval.txt typo for settabwinvar method call (matches latest Vim).

runtime/doc/eval.txt

@@ -2992,7 +2992,11 @@ bufadd({name})						*bufadd()*
 		number.  Otherwise return the buffer number of the newly
 		created buffer.  When {name} is an empty string then a new
 		buffer is always created.
-		The buffer will not have' 'buflisted' set.
+		The buffer will not have 'buflisted' set and not be loaded
+		yet.  To add some text to the buffer use this: >
+			let bufnr = bufadd('someName')
+			call bufload(bufnr)
+			call setbufline(bufnr, 1, ['some', 'text'])
 <		Can also be used as a |method|: >
 			let bufnr = 'somename'->bufadd()
 
@@ -8704,7 +8708,7 @@ setline({lnum}, {text})					*setline()*
 		Can also be used as a |method|, passing the text as the base: >
 			GetText()->setline(lnum)
 
-setloclist({nr}, {list}[, {action}[, {what}]])		*setloclist()*
+setloclist({nr}, {list} [, {action} [, {what}]])		*setloclist()*
 		Create or replace or add to the location list for window {nr}.
 		{nr} can be the window number or the |window-ID|.
 		When {nr} is zero the current window is used.
@@ -8720,6 +8724,10 @@ setloclist({nr}, {list}[, {action}[, {what}]])		*setloclist()*
 		only the items listed in {what} are set. Refer to |setqflist()|
 		for the list of supported keys in {what}.
 
+		Can also be used as a |method|, the base is passed as the
+		second argument: >
+			GetLoclist()->setloclist(winnr)
+
 setmatches({list} [, {win}])				*setmatches()*
 		Restores a list of matches saved by |getmatches() for the
 		current window|.  Returns 0 if successful, otherwise -1.  All
@@ -8728,6 +8736,9 @@ setmatches({list} [, {win}])				*setmatches()*
 		If {win} is specified, use the window with this number or
 		window ID instead of the current window.
 
+		Can also be used as a |method|: >
+			GetMatches()->setmatches()
+<
 							*setpos()*
 setpos({expr}, {list})
 		Set the position for String {expr}.  Possible values:
@@ -8777,8 +8788,10 @@ setpos({expr}, {list})
 		also set the preferred column.  Also see the "curswant" key in
 		|winrestview()|.
 
+		Can also be used as a |method|: >
+			GetPosition()->setpos('.')
 
-setqflist({list} [, {action}[, {what}]])		*setqflist()*
+setqflist({list} [, {action} [, {what}]])		*setqflist()*
 		Create or replace or add to the quickfix list.
 
 		If the optional {what} dictionary argument is supplied, then
@@ -8887,7 +8900,10 @@ setqflist({list} [, {action}[, {what}]])		*setqflist()*
 		independent of the 'errorformat' setting.  Use a command like
 		`:cc 1` to jump to the first position.
 
-
+		Can also be used as a |method|, the base is passed as the
+		second argument: >
+			GetErrorlist()->setqflist()
+<
 							*setreg()*
 setreg({regname}, {value} [, {options}])
 		Set the register {regname} to {value}.
@@ -8944,6 +8960,10 @@ setreg({regname}, {value} [, {options}])
 		nothing: >
 			:call setreg('a', '', 'al')
 
+<		Can also be used as a |method|, the base is passed as the
+		second argument: >
+			GetText()->setreg('a')
+
 settabvar({tabnr}, {varname}, {val})			*settabvar()*
 		Set tab-local variable {varname} to {val} in tab page {tabnr}.
 		|t:var|
@@ -8952,6 +8972,9 @@ settabvar({tabnr}, {varname}, {val})			*settabvar()*
 		Tabs are numbered starting with one.
 		This function is not available in the |sandbox|.
 
+		Can also be used as a |method|, the base is used as the value: >
+			GetValue()->settabvar(tab, name)
+
 settabwinvar({tabnr}, {winnr}, {varname}, {val})	*settabwinvar()*
 		Set option or local variable {varname} in window {winnr} to
 		{val}.
@@ -8968,6 +8991,9 @@ settabwinvar({tabnr}, {winnr}, {varname}, {val})	*settabwinvar()*
 			:call settabwinvar(3, 2, "myvar", "foobar")
 <		This function is not available in the |sandbox|.
 
+		Can also be used as a |method|, the base is used as the value: >
+			GetValue()->settabwinvar(tab, winnr, name)
+
 settagstack({nr}, {dict} [, {action}])			*settagstack()*
 		Modify the tag stack of the window {nr} using {dict}.
 		{nr} can be the window number or the |window-ID|.
@@ -9001,6 +9027,8 @@ settagstack({nr}, {dict} [, {action}])			*settagstack()*
 			call settagstack(1003, stack)
 			unlet stack
 <
+		Can also be used as a |method|, the base is used as the Dict: >
+			GetStack()->settagstack(winnr)
 
 setwinvar({nr}, {varname}, {val})			*setwinvar()*
 		Like |settabwinvar()| for the current tab page.
@@ -9008,10 +9036,16 @@ setwinvar({nr}, {varname}, {val})			*setwinvar()*
 			:call setwinvar(1, "&list", 0)
 			:call setwinvar(2, "myvar", "foobar")
 
+<		Can also be used as a |method|, the base is used as the value: >
+			GetValue()->setwinvar(winnr, name)
+
 sha256({string})						*sha256()*
 		Returns a String with 64 hex characters, which is the SHA256
 		checksum of {string}.
 
+		Can also be used as a |method|: >
+			GetText()->sha256()
+
 shellescape({string} [, {special}])			*shellescape()*
 		Escape {string} for use as a shell command argument.
 
@@ -9043,6 +9077,8 @@ shellescape({string} [, {special}])			*shellescape()*
 		    :call system("chmod +w -- " . shellescape(expand("%")))
 <		See also |::S|.
 
+		Can also be used as a |method|: >
+			GetCommand()->shellescape()
 
 shiftwidth([{col}])						*shiftwidth()*
 		Returns the effective value of 'shiftwidth'. This is the
@@ -9065,6 +9101,9 @@ shiftwidth([{col}])						*shiftwidth()*
 		'vartabstop' feature. If no {col} argument is given, column 1
 		will be assumed.
 
+		Can also be used as a |method|: >
+			GetColumn()->shiftwidth()
+
 sign_ functions are documented here: |sign-functions-details|
 
 simplify({filename})					*simplify()*