vim-patch:0cc5dce: runtime(doc): clarify directory of Vim's executable vs CWD

According to :h win32-PATH, "the same directory as Vim" means the same
directory as the Vim executable, not Vim's current directory.  In patch
8.2.4860 these two concepts were mixed up.

closes: vim/vim#15451

0cc5dce578

src/nvim/eval.lua

@@ -2059,8 +2059,10 @@ M.funcs = {
       This function checks if an executable with the name {expr}
       exists.  {expr} must be the name of the program without any
       arguments.
+
       executable() uses the value of $PATH and/or the normal
-      searchpath for programs.		*PATHEXT*
+      searchpath for programs.
+      					*PATHEXT*
       On MS-Windows the ".exe", ".bat", etc. can optionally be
       included.  Then the extensions in $PATHEXT are tried.  Thus if
       "foo.exe" does not exist, "foo.exe.bat" can be found.  If
@@ -2070,8 +2072,13 @@ M.funcs = {
       then the name is also tried without adding an extension.
       On MS-Windows it only checks if the file exists and is not a
       directory, not if it's really executable.
-      On Windows an executable in the same directory as Vim is
-      always found (it is added to $PATH at |startup|).
+      On MS-Windows an executable in the same directory as the Vim
+      executable is always found (it's added to $PATH at |startup|).
+      			*NoDefaultCurrentDirectoryInExePath*
+      On MS-Windows an executable in Vim's current working directory
+      is also normally found, but this can be disabled by setting
+      the $NoDefaultCurrentDirectoryInExePath environment variable.
+
       The result is a Number:
       	1	exists
       	0	does not exist