Add missing conversions from other types to f32 in fround.
Restrict fround() to only float, double, signed, unsigned (no unions / intish).
Restrict Bitwise operations to intish, particularly |0, when not applied to a foreign function.

Adding more exhaustive tests of stdlib Math, move to a separate file.
Adding tests of interesting values for the stdlib asm.js functions.

BUG= https://bugs.chromium.org/p/v8/issues/detail?id=4203
TEST=test-asm-validator,asm-wasm
R=titzer@chromium.org,rossberg@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1804243003

Cr-Commit-Position: refs/heads/master@{#34967}