* insns.def: fix regexp's once option behavior.
  fix [ruby-trunk - Bug #6701]
* insns.def: remove `onceinlinecache' and introduce `once' instruction.
  `once' doesn't use `setinlinecache' insn any more.
* vm_core.h: `union iseq_inline_storage_entry' to store once data.
* compile.c: catch up above changes.
* iseq.c: ditto.
* vm.c, vm_insnhelper.c: ditto. fix `m_core_set_postexe()' which
  is depend on `onceinlinecache' insn.
* test/ruby/test_regexp.rb: add tests.
* iseq.c: ISEQ_MINOR_VERSION to 1 (should increment major?)



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42637 b2dd03c8-39d4-4d8f-98ff-823fe69b080e