Add RELEASE_ASSERT (and a few friends)
https://bugs.webkit.org/show_bug.cgi?id=107725

Reviewed by Filip Pizlo.

Adding a few macros to make release mode assertions easier and more readable.
Also makes same assertions more useful in debug builds.

* wtf/Assertions.h:

git-svn-id: svn://svn.chromium.org/blink/trunk@140577 bbb929c8-8fbe-4397-9dbb-9b2b20218538