[Cocoa] Enable the compiler to check format strings specified with UI_STRING and UI_STRING_KEY
https://bugs.webkit.org/show_bug.cgi?id=140003

Reviewed by Darin Adler.

* Misc/WebLocalizableStrings.h: Made UI_STRING and UI_STRING_KEY call a new helper function
that takes their "string" parameter as a "value" "parameter and has an attribute telling
the compiler that if the "value" parameter is a format string then the function returns a
modified version of it. The result is that if UI_STRING is used as a format string parameter
to some function or method, the compiler will check the format specifiers in the string
against the other parameters.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@177825 268f45cc-cd09-0410-ab3c-d52691b4dbfc