inc/crt/sys/types.bi: Provide off_t on Windows too, like MinGW

Both MinGW.org and MinGW-w64 headers provide the off_t type, which is also
used by many C libraries. I.e. we need it for FB bindings.

Not to be confused with the msvcrt _off_t type, which apparently is always
32bit, while the POSIX off_t depends on _FILE_OFFSET_BITS.
inc: Allegro 4.4.2, algif 1.3, alpng 1.3
inc: Allegro 5.0.10
examples: Add Allegro 5 example
examples: Add IUP text box example