Take upstream libm changes.

Mostly workarounds for GCC and Clang bugs.

Change-Id: I4ef428a42d4ac6d622659053711a8cc416925727
diff --git a/libm/upstream-freebsd/lib/msun/src/s_log1p.c b/libm/upstream-freebsd/lib/msun/src/s_log1p.c
index b062a8a..3cc77bd 100644
--- a/libm/upstream-freebsd/lib/msun/src/s_log1p.c
+++ b/libm/upstream-freebsd/lib/msun/src/s_log1p.c
@@ -96,6 +96,7 @@
 Lp7 = 1.479819860511658591e-01;  /* 3FC2F112 DF3E5244 */
 
 static const double zero = 0.0;
+static volatile double vzero = 0.0;
 
 double
 log1p(double x)
@@ -109,7 +110,7 @@
 	k = 1;
 	if (hx < 0x3FDA827A) {			/* 1+x < sqrt(2)+ */
 	    if(ax>=0x3ff00000) {		/* x <= -1.0 */
-		if(x==-1.0) return -two54/zero; /* log1p(-1)=+inf */
+		if(x==-1.0) return -two54/vzero; /* log1p(-1)=+inf */
 		else return (x-x)/(x-x);	/* log1p(x<-1)=NaN */
 	    }
 	    if(ax<0x3e200000) {			/* |x| < 2**-29 */
@@ -173,3 +174,7 @@
 	if(k==0) return f-(hfsq-s*(hfsq+R)); else
 		 return k*ln2_hi-((hfsq-(s*(hfsq+R)+(k*ln2_lo+c)))-f);
 }
+
+#if (LDBL_MANT_DIG == 53)
+__weak_reference(log1p, log1pl);
+#endif