Expand documentation of common-utils.h::FUNCTION_NAME

While looking at this macro, I noticed that it wasn't always necessarily
defined. That prompted me to search the current sources to make sure
that all uses were adequately protected, which they were. But to help
prevent future uses to be made unprotected, this patch expands the
current macro documentation a bit.

gdb/ChangeLog:

        * common/common-utils.h (FUNCTION_NAME): Expand the macro's
        documentation a bit.
Add ARI (ok) marker for __func__ reference in common-utils.h

The ARI script flagged the use of the __func__ variable, which
is normally not allowed (not defined in C90). However, this particular
use is OK, as the reference is only made when __STDC_VERSION__ >=
199901L.  So, add an "ARI:" comment to explicitly OK this use.

gdb/ChangeLog:

        * common/common-utils.h: Add "ARI:" comment beside __func__
        reference.
Comment typo

	* elf64-ppc.c (STK_LINKER): Comment typo fix.
Fix gas build breakage

	* config/tc-tic4x.c (md_shortopts): s/CONST/const/.
Display the reference causing a shared library to be needed

Adds a section for --as-needed libraries to a linker map file, similar
to what we do for archive libraries.

bfd/
	* elflink.c (elf_link_add_object_symbols): Call minfo for --as-needed.
ld/
	* ldlang.c (asneeded_list_head, asneeded_list_tail): New vars.
	(lang_init): Initialise them.
	(lang_print_asneeded): New function.
	(lang_process): Call lang_print_asneeded.
	* ldlang.h (struct asneeded_minfo): New.
	(asneeded_list_tail): Declare.
	* ldmain.c (add_archive_element): Improve archive map heading.
	* ldmisc.c (minfo): Stash --as-needed info.