For UTF-16, the line-length limit is set to 2/3th of the line length limit for other text, because UTF-16 -> UTF-8 conversion can increase the line length (in bytes) by max 50%. This guarantees that a UTF-16 diff can be made by converting the two UTF-16 files to UTF-8 and then do a normal diff.

re-use looks_like_blob

Trying to commit a file with an UTF-16 BOM will now give a warning, just as a file containing crlf

The --args command line option now accept UTF-16 files as well

src/stash.c: In function ‘stash_cmd’:
src/stash.c:377:16: warning: ‘stashid’ may be used uninitialized in this function
src/stash.c:472:7: note: ‘stashid’ was declared here

Implement looks_like_text(), similar to looks_like_binary() but it can distinguish more types of text/binary files.

This has the effect that on Windows wiki pages can now be in unicode as well.

This has the effect that on Windows the --args file accepts a unicode file, starting with a UTF-16 BOM as well

checkin.c: Make limits the same as in looks_like_binary(), preparation to move the function to diff.c

struct utimbuf -> struct _utimbuf (compiler warning with mingw-w64)

a few "const" additions (lower memory footprint, allows C-compiler to optimize better)

struct utimbuf -> struct _utimbuf (compiler warning with mingw-w64)

a few "const" additions