ENH: remove obsolete ifort flags

I removed obsolete ifort flags on windows (they were so old that I could not find any help on their meaning).

I removed the fragile CPU-specific code, and instead use sensible default (I think): code is generated to work on the most common architecture, with optimized code path generated for relatively recent ones (SSE3 on ia32, no optimization on amd64).

This allowed me to build scipy 0.12.0 and run the test suite without any error on both win32 and win64 (using vs 2008 and ifort + MKL).

David