Removing dead Makefile stubs for generated code

While wrapping up the release, I noticed that Makefile.comm-armci
is still here in spite of ARMCI support being retired in r20289.
Pavan Balaji just stumbled across Makefile.comm-mpi which reminded
me to actually pull these, along with pvm.



git-svn-id: http://svn.code.sf.net/p/chapel/code/trunk@22148 3a8e244f-b0f2-452b-bcba-4c88e055c3ca