[PATCH libquadmath, pr68686] tgammaq(x) is always negative for noninteger x < 0

[Ed Smith-Rowland]

Here is a patch for tammaq for negative argument pr68686.

I know about depending on ports from upstream but this was done recently 
and this (tgammaq) was left out.

This patch is basically a one-liner.

I have test cases but libquadmath doesn't have a testsuite.

One test just shows alternating signs for -0.5Q, -1.5Q, -2.5Q, etc.

Another test verifies the Gamma reflection formula:

 Â tgamma(1-x) * tgamma(x) - pi / sinq(pi*x) is tiny.

Builds on x86_64-linux and tests correctly offline.


OK?


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2017-11-10  Edward Smith-Rowland  <3dw4rd@verizon.net>

	PR libquadmath/68686
	* math/tgammaq.c: Correct sign for negative argument.
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