libsframe: remove sframe_get_funcdesc_with_addr API

libsframe: remove sframe_get_funcdesc_with_addr API

This is an incompatible ABI change in libsframe.

The interface provided by this function is not a healthy abstraction to
expose: the return type sframe_func_desc_entry, which is defined in
include/sframe.h (the SFrame binary format definition).  This ties up
the library in a undesirable way.  Most importantly, this function
should technically not be directly necessary for a stack tracer.  A
stack tracer will likely only need to do a sframe_find_fre ().

Rename the API to continue to use the functionality internally in the
library.  bfd/linker does not use this function.

Change the return type of the previous definition and make a note about
its planned deprecation.

include/
	* sframe-api.h:  Change return type of sframe_get_funcdesc_with_addr.
	Add comment for intention to deprecate.
libsframe/
	*sframe.c (sframe_get_funcdesc_with_addr): Change return type
	and set error code. This API is deprecated.
        (sframe_get_funcdesc_with_addr_internal): New definition for
	internal use.
	(sframe_find_fre): Use sframe_get_funcdesc_with_addr_internal
	instead.