vim-patch:8.2.0928: many type casts are used for vim_strnsave()

Problem:    Many type casts are used for vim_strnsave().
Solution:   Make the length argument size_t instead of int. (Ken Takata,
            closes vim/vim#5633)  Remove some type casts.
df44a27b53

N/A patches for version.c:

vim-patch:8.2.0315: build failure on HP-UX system

Problem:    Build failure on HP-UX system.
Solution:   Use LONG_LONG_MIN instead of LLONG_MIN.  Add type casts for switch
            statement. (John Marriott)
c593bec412

vim-patch:8.2.1052: build failure with older compilers

Problem:    Build failure with older compilers.
Solution:   Move declaration to start of block.
7acde51832

vim-patch:8.2.2229: build failure without the +eval feature

Problem:    build failure without the +eval feature.
Solution:   Add #ifdef.
39cb2dab18

vim-patch:8.2.2232: compiler error for falling through into next case

Problem:    Compiler error for falling through into next case.
Solution:   Move FALLTHROUGH below the #endif
9618a25b9c

src/nvim/fileio.c

@@ -2032,7 +2032,7 @@ static char_u *next_fenc(char_u **pp, bool *alloced)
     r = enc_canonize(*pp);
     *pp += STRLEN(*pp);
   } else {
-    r = vim_strnsave(*pp, (int)(p - *pp));
+    r = vim_strnsave(*pp, p - *pp);
     *pp = p + 1;
     p = enc_canonize(r);
     xfree(r);