Fix PR target/63408

The attached patch fixes PR target/63408 and adds a regression test
for the same. The problem is essentially that
vfp3_const_double_for_fract_bits() needs to be aware that negative
values cannot be used in this context.

Tested with a bootstrap and regression test run on armhf. Applied.




2015-06-24  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>

	PR target/63408
	* config/arm/arm.c (vfp3_const_double_for_fract_bits): Disable
	for negative numbers.

2015-06-24  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>

	PR target/63408
	* gcc.target/arm/pr63408.c: New test.

From-SVN: r224879