The MACHTYPE bash variable is an odd thing that returns e.g.
x86_64-redhat-linux-gnu on a CentOS system, but x86_64-pc-linux-gnu
on a Debian system, and possibly something different on other distros.
mach valgrind-test is the only place actually relying on MACHTYPE.
Others rely on information from python modules. Uniformize that, and use
the more generic 'pc' rather than 'redhat'.
--HG--
rename : build/valgrind/i386-redhat-linux-gnu.sup => build/valgrind/i386-pc-linux-gnu.sup
rename : build/valgrind/x86_64-redhat-linux-gnu.sup => build/valgrind/x86_64-pc-linux-gnu.sup
extra : rebase_source : ad94ce69e8094d2b9ddae97a3d261945886c0a61