[Commit]: Add debuglink support to objdump and readelf

[Joseph Myers]

This patch causes problems for glibc linknamespace tests because of how it 
changes the output format of readelf on .a files.

Previously, "readelf -W -s libc.a" would produce output starting e.g.:

File: /scratch/jmyers/glibc/many8/build/glibcs/x86_64-linux-gnu/glibc/libc.a(init-first.o)

Symbol table '.symtab' contains 30 entries:

and continuing with symbol information for each object in that .a file.  
After this commit, instead it starts:

File: /scratch/jmyers/glibc/many8/build/glibcs/x86_64-linux-gnu/glibc/libc.a

Symbol table '.symtab' contains 30 entries:

and every object's symbol information starts with the same File: line, 
missing any information about which object's symbols (within libc.a) are 
being listed.

I think the previous File: lines that said libc.a(init-first.o) etc., 
identifying the particular object within libc.a, were clearly preferable, 
and the glibc linknamespace tests rely on having that information about 
the individual object within libc.a.

-- 
Joseph S. Myers
joseph@codesourcery.com