Merge Ruby r46881

re_pattern_buffer: shrink from 464 to 448 bytes on 64-bit

* include/ruby/oniguruma.h (struct re_pattern_buffer): shrink to 448
  bytes from 464 bytes on 64-bit.  This breaks the ABI.
  [Feature #10034]

Reducing struct re_pattern_buffer from 464 to 448 bytes allows it to fit
into neatly into seven 64-byte cache lines on x86-64 systems.
Merge branch 'ruby-2.x' into ruby-2.x-buildenv