signal.c: extract check_stack_overflow
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39356 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
signal.c: extract check_stack_overflow
of declaration-after-statement. [Bug #5014]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39356 b2dd03c8-39d4-4d8f-98ff-823fe69b080e