Revert "v8: Fix build in ISO C++ 11 mode"

This reverts commit 8db2b6bd311106e7e45cc2cb40f39715e999a986.
Revert "v8: Replace check for hardfloat vs. softfloat"

This reverts commit 24807318f13ed2f41cfa4f74918e9c4923f4f3f1.