Guard against stack overflow in Runtime::StringReplaceOneCharWithString.

Unfortunately, this only triggers with "ulimit -s 1024" (or less), so we
cannot have an mjsunit test. The test that fails is
test/mjsunit/string-replace-one-char.js on x64.debug.

R=ishell@chromium.org
BUG=

Review URL: https://codereview.chromium.org/264383006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21262 ce2b1a6d-e550-0410-aec6-3dcde31c8c00