Add conditional support for noreturn functions.

This adds support for tagging functions with the noreturn attribute.
If DO_CRASH is enabled then ast_do_crash never returns.  If AST_DEVMODE
and DO_CRASH are enabled then failed assertions never return.  This can
resolve a large number of false positives with static analyzers.

ASTERISK-26220 #close

Change-Id: Icfb61e5fe54574eced4c3e88b317244f467ec753