When --optimize-for-size is true, the prologue generation outputs the
pre-aging code stub address directly to the instruction stream.  Previously
this was done using dd() which failed if there was any pending constant
pool entries left to be written.  This CL introduces an emit_code_stub_address()
for this purpose instead.

BUG=v8:2968
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/47743007

Patch from Ross McIlroy <rmcilroy@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17485 ce2b1a6d-e550-0410-aec6-3dcde31c8c00