configure: accept ppc[64] as alias for powerpc[64] in gcc tuples
apparently some distros use this form, and it seems to be supported in
the gcc build system.
diff --git a/configure b/configure
index 997e665..6310e0b 100755
--- a/configure
+++ b/configure
@@ -320,8 +320,8 @@
mips*) ARCH=mips ;;
microblaze*) ARCH=microblaze ;;
or1k*) ARCH=or1k ;;
-powerpc64*) ARCH=powerpc64 ;;
-powerpc*) ARCH=powerpc ;;
+powerpc64*|ppc64*) ARCH=powerpc64 ;;
+powerpc*|ppc*) ARCH=powerpc ;;
sh[1-9bel-]*|sh|superh*) ARCH=sh ;;
s390x*) ARCH=s390x ;;
unknown) fail "$0: unable to detect target arch; try $0 --target=..." ;;