Include Bug 53001 in GCC 4.9 Changes

[Joshua J Cogliati]

I request that Bug 53001 (
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53001) be mentioned in the
http://gcc.gnu.org/gcc-4.9/changes.html

This change adds a flag -Wfloat-conversion to C-family gcc.

Possible text for the changes page:

The -Wfloat-conversion option has been added for the C and C++
compilers, which warns about the subset of -Wconversion conversions that
include floating point loss of precision, including automatic conversion
of floating point into integers and floating point conversions from
higher precision to lower precision.

Josh Cogliati