Audit split(1)

1) Refactor manpage, add STANDARDS section.
2) Boolean-style-changes.
3) Update usage, reflecting num-idiom also changed in the manpage.
4) Refactor error messages.
5) Also fclose stdin.
6) Empty line before return.

README

@@ -56,7 +56,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 #*| printf          yes                          none
 =*| pwd             yes                          none
 =   readlink        non-posix                    none
-=*  renice          yes                          none
+=*| renice          yes                          none
 =*| rm              yes                          none (-i)
 =*| rmdir           yes                          none
 #   sed
@@ -67,7 +67,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*| sha512sum       non-posix                    none
 =*| sleep           yes                          none
     sort            no                           -m, -o, -d, -f, -i
-=*  split           yes                          none
+=*| split           yes                          none
 =*| sponge          non-posix                    none
 #*  strings         yes                          none
 =*  sync            non-posix                    none