Fix finite-math-only lgamma functions signgam setting (bug 19211).

The lgamma inline functions in bits/math-finite.h do not set signgam
if __USE_ISOC99, even when other feature test macros mean a standard
such as XSI POSIX is selected for which it should be set.  (This is
essentially the opposite issue to bug 15421, the out-of-line versions
setting signgam even when they shouldn't.)

This patch fixes those functions to use __USE_MISC || __USE_XOPEN as
the condition for when to set signgam, since it's the condition for
when math.h declares signgam.  The legacy gamma* names are only
declared at all if __USE_MISC || __USE_XOPEN, so they just set signgam
unconditionally.

Tests for certain standards or not using _GNU_SOURCE cannot use
test-skeleton.c (this is a known issue noted on the wiki todo list).
Thus, the new tests that signgam remains not set in ISO C modes do not
use test-skeleton.c.  They also define _ISOMAC to avoid running into
declarations in the internal include/ headers that only work in
_GNU_SOURCE mode.

Tested for x86_64 and x86.

	[BZ #19211]
	* math/bits/math-finite.h (lgamma): Set signgam if [__USE_MISC ||
	__USE_XOPEN], not if [!__USE_ISOC99].
	(lgammaf): Likewise.
	(lgammal): Likewise.
	(gamma): Set signgam unconditionally, not if [!__USE_ISOC99].
	(gammaf): Likewise.
	(gammal): Likewise.
	* math/test-signgam-finite-c11.c: New file.
	* math/test-signgam-finite-c99.c: Likewise.
	* math/test-signgam-finite.c: Likewise.
	* math/Makefile (tests): Add test-signgam-finite,
	test-signgam-finite-c99 and test-signgam-finite-c11.
	(CFLAGS-test-signgam-finite.c): New variable.
	(CFLAGS-test-signgam-finite-c99.c): Likewise.
	(CFLAGS-test-signgam-finite-c11.c): Likewise.

1 files changed, 1 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index 901f92b4cc..b462e85ddc 100644
--- a/NEWS
+++ b/NEWS
@@ -22,7 +22,7 @@ Version 2.23
   19003, 19007, 19012, 19016, 19018, 19032, 19046, 19048, 19049, 19050,
   19059, 19071, 19074, 19076, 19077, 19078, 19079, 19085, 19086, 19088,
   19094, 19095, 19124, 19125, 19129, 19134, 19137, 19156, 19174, 19181,
-  19189, 19201, 19205, 19209, 19212.
+  19189, 19201, 19205, 19209, 19211, 19212.
 
 * A defect in the malloc implementation, present since glibc 2.15 (2012) or
   glibc 2.10 via --enable-experimental-malloc (2009), could result in the