Remove redundant osmesa shared library install from Makefile.old

Remove redundant osmesa shared library install from Makefile.old

Since osmesa now has been converted to Makefile.am, an appropriate install: rule
is generated to install the shared libary, so we no longer need to do that in
src/mesa/Makefile.old

This leaves nothing in src/mesa/Makefile.old but the tags: rule, so move that to
Makefile.am and remove Makefile.old

Also, nothing now uses OSMESA_LIB_GLOB anymore, so remove it

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Eric Anholt <eric@anholt.net>