Fix negative fixed-point->float conversions The fixed-to-float conversion routine in mathutils only operated correctly on positive numbers. This caused failures in some GLES1 apps when negative fixed-point values were converted, as for glTranslatex(). Bug: b/199919700 Test: Manual -- Zillow app should show data on map Change-Id: I2ac4794478d3ad4c50057527134c9c17c8680338 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3209826 Reviewed-by: Ian Elliott <ianelliott@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Mark Lobodzinski <mark@lunarg.com> Commit-Queue: Ian Elliott <ianelliott@google.com>