Parser: Refactor strict mode checks for functions

Moves the strict mode checks and error reporting for the function and
parameter names into a separate CheckStrictFunctionNameAndParameters()
function in ParserBase. Parsing of arrow functions will then use this
new function instead of duplicating the error code.

BUG=
R=marja@chromium.org

Review URL: https://codereview.chromium.org/332053004

Patch from Adrián Pérez de Castro <aperez@igalia.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21896 ce2b1a6d-e550-0410-aec6-3dcde31c8c00