Reuse (shared) cachegrind source files in callgrind directly.

The callgrind Makefile.am had a common sources list that included
../cachegrind/cg_arch.c. This doesn't play well with automake and
subdir-objects. Especially make distclean was broken because some
.deps files were removed multiple times.

Just include the shared source file directly into the callgrind
source file that needs it (cg_arch.c in sim.c).

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13528 a5019735-40e9-0310-863c-91ae7b9d1cf9