Add comments in opcode.h

Fix indents in opcode.h.

add the name 'Narihiro Nakamura'

Refactor codes using REGEXP_CLASS define.

Replace mrb_intern() func with mrb_intern2() or mrb_intern_cstr() func.

Replace mrb_intern() with mrb_intern_cstr().

Replace 0 with '\0' as nul terminated string.

Refactor true_or() and false_and() in object.c.

Fix matching the host platform on the androideabi toolchain on windows.

The included method of determining the host platform in the androideabi
would not match to windows if RUBY_PLATFORM returned mingw, wince, or
emx. As an added pre-caution, using a case statement with regexp
matching will better determine the host platform since it won't be case
sensitive and for windows is set to match more specifially than just
"win".

call Class#inherited when Class.new(klass)

khash.h optimizes more.

Change parameter type to suppress -Wsign-compare warnings

kh_resize_##name bug fixed.