[X86] Add a 32-bit command line with only sse2 to vector-sext.ll and...

[X86] Add a 32-bit command line with only sse2 to vector-sext.ll and vector-sext.ll to show some of the scalarized load sequences without 64-bit scalar support.

Some of these sequeces look pretty bad since we have to copy the sign bit from a 32 bit register to a 64 bit register to finish a sign extend.

llvm-svn: 347175