Merged r15665 into 3.18 branch.

Use internal array as API function cache.

R=yangguo@chromium.org
BUG=chromium:260106
TEST=cctest/test-api/Regress260106

Review URL: https://codereview.chromium.org/19793004

git-svn-id: https://v8.googlecode.com/svn/branches/3.18@15767 ce2b1a6d-e550-0410-aec6-3dcde31c8c00