Revert "aom_encoder: enable floating point exceptions" This reverts commit 48c10c7d917b75d6521c54be700e1227c1647d5d. Reason for revert: this incorrectly detects feenableexcept for i686-w64-mingw32 (at least), causing the link to fail BUG=aomedia:388 Change-Id: I141fec2285bd67d1312f1eb6be528cc69108cd27