This fixes the signatures of "Math.ceil", "Math.floor" and "Math.sqrt"
from "(float?) -> float" to "(float?) -> floatish" which avoids using a
resulting float value without coercing the value via explicit "fround"
annotations. This ensures proper ECMAScript semantics are maintained.

R=clemensh@chromium.org
TEST=mjsunit/regress/regress-6838-2
BUG=v8:6838

Change-Id: Ib5821641265bc862184adb270e8dbf8c703fdfb0
Reviewed-on: https://chromium-review.googlesource.com/681694Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48142}