Use inttypes.h

Use PRI[dux]PTR defined in inttypes.h.

(Merged from Ruby 2.x.)
Use PRIuPTR instead of PRIuSIZE

VC12 doesn't support PRIuSIZE.
Use PRIdPTR
Fix coding style
Restore comments from Oniguruma 5.9.0
Fix type mismatch
Merge branch 'topic/inttypes'