Take upstream libm changes.

Mostly workarounds for GCC and Clang bugs.

Change-Id: I4ef428a42d4ac6d622659053711a8cc416925727
diff --git a/libm/upstream-freebsd/lib/msun/src/s_expm1f.c b/libm/upstream-freebsd/lib/msun/src/s_expm1f.c
index fb37494..c0a3934 100644
--- a/libm/upstream-freebsd/lib/msun/src/s_expm1f.c
+++ b/libm/upstream-freebsd/lib/msun/src/s_expm1f.c
@@ -23,7 +23,6 @@
 
 static const float
 one		= 1.0,
-huge		= 1.0e+30,
 tiny		= 1.0e-30,
 o_threshold	= 8.8721679688e+01,/* 0x42b17180 */
 ln2_hi		= 6.9313812256e-01,/* 0x3f317180 */
@@ -37,6 +36,8 @@
 Q1 = -3.3333212137e-2,		/* -0x888868.0p-28 */
 Q2 =  1.5807170421e-3;		/*  0xcf3010.0p-33 */
 
+static volatile float huge = 1.0e+30;
+
 float
 expm1f(float x)
 {