PowerPC: Add detection of SPE (found on e500) and VSX

Poky (Yocto's reference distro) has a special build for the e500v2, so
I'm guessing this ABI is somewhat important.

Change-Id: I14839ba5678944c2864bffff14176c4d61b8799f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

config.tests/arch/arch.cpp

@@ -275,6 +275,12 @@ const char msg2[] = "==Qt=magic=Qt== Sub-architecture:"
 // -- POWER, PowerPC --
 #ifdef __ALTIVEC__
 " altivec"
+#endif
+#ifdef __SPE__
+" spe"
+#endif
+#ifdef __VSX__
+" vsx"
 #endif
                    "";