Replace ast_say_* functionn with function pointers, so that modules

can override them.
On passing, fix a potential problem in the top level Makefile:

if a static library is not referenced by any of the core objects,
it is not linked in the main program, and will not be available
to modules, which leads to failure at runtime when the modules
are loaded.
This is the case of stdtime/localtime.o, which supplies some core
symbolx, but is only linked in as a library. Fix the problem by
linking in the object.

NOTE: this is intended as a temporary aid to replace the
existing say.c with a newer implementation. Once the
task is completed, we may decide whether or not the ast_say*()
functions should be pluggable or not and possibly revert
part of this change.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@14382 65c4cc65-6c06-0410-ace0-fbb531ad65f3