Push FPDenormMode, FPOperationMode to the end

Push FPDenormMode, FPOperationMode to the end

This is a cosmetic change for the benefit of generating the SPIR-V spec.
It reorders the "FP Denorm Mode" and "FP Operation Mode" so they are
the last sections in chapter 3 before the instruction listing.
They become 3.37 and 3.38. The idea is to preserve the section numbering
for earlier sections. For example, keep 3.31 as the Capability section.