configure: allow post-fixed cpu strings for athlon64, k8, and opteron

when setting the -march flag.

This is to match gcc's {athlon64,k8,opteron}-sse3 -march flags.
Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>

configure

@@ -2233,7 +2233,7 @@ elif enabled x86; then
             disable cmov
         ;;
         # targets that do support conditional mov (cmov)
-        i686|pentiumpro|pentium[23]|pentium-m|athlon|athlon-tbird|athlon-4|athlon-[mx]p|athlon64|k8|opteron|athlon-fx|core2|amdfam10|barcelona|atom)
+        i686|pentiumpro|pentium[23]|pentium-m|athlon|athlon-tbird|athlon-4|athlon-[mx]p|athlon64*|k8*|opteron*|athlon-fx|core2|amdfam10|barcelona|atom)
             cpuflags="-march=$cpu"
             enable cmov
             enable fast_cmov