remove unneeded amd64-specific compiler directives The compiler directive "-mfpmath=sse" is amd64-specific. On i386 is just generates a harmless gcc warning but it causes a FTBFS on ppc (and presumably other architectures). The test suite checks for #578004 anyway (which this directive was added to work around) and the "-mfpmath=sse" is the default on amd64.
