re.c: rb_reg_region_copy

* re.c (rb_reg_region_copy): new function to try with GC if copy
  failed and return the error.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48672 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
parse.y: check single regexp only

* parse.y (regexp_contents): check in ripper only if the whole
  content is a single regexp without interpolation.
  [ruby-dev:48714] [Bug #10437]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48673 b2dd03c8-39d4-4d8f-98ff-823fe69b080e