Revert "[CLANG][PATCH][FPEnv] Add support for option -ffp-eval-method and...

Revert "[CLANG][PATCH][FPEnv] Add support for option -ffp-eval-method and extend #pragma float_control similarly"
The intent of this patch is to add support of -fp-model=[source|double|extended] to allow
the compiler to use a wider type for intermediate floating point calculations. As a side
effect to that, the value of FLT_EVAL_METHOD is changed according to the pragma
float_control.
Unfortunately some issue was uncovered with this change in preprocessing. See details in
https://reviews.llvm.org/D93769 . We are therefore reverting this patch until we find a way
to reconcile the value of FLT_EVAL_METHOD, the pragma and the -E flow.

This reverts commit 66ddac22.