Update to FreeBSD libm r336665.

This reverts commit 253a8306316cedfd6fd3e3a169fbffe4cac04035 and moves
us forward to a revision that contains fixes for the problem with the
previous attempt.

This also makes sincos(3)/sincosf(3)/sincosl(3) available to `_BSD_SOURCE`
as well as `_GNU_SOURCE`.

The new FreeBSD libm code requires the FreeBSD `__CONCAT` macro, and all
our existing callers are FreeBSD too, so update that.

There's also an assumption that <complex.h> drags in <math.h> which isn't
true for us, so work around that with `-include` in the makefile. This
then causes clang to recognize a bug -- returning from a void function --
in our fake (LP32) sincosl(3), so fix that too.

Bug: http://b/111710419
Change-Id: I84703ad844f8afde6ec6b11604ab3c096ccb62c3
Test: ran tests
diff --git a/libm/upstream-freebsd/lib/msun/src/e_hypot.c b/libm/upstream-freebsd/lib/msun/src/e_hypot.c
index 2398e98..0c16767 100644
--- a/libm/upstream-freebsd/lib/msun/src/e_hypot.c
+++ b/libm/upstream-freebsd/lib/msun/src/e_hypot.c
@@ -12,7 +12,7 @@
  */
 
 #include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
+__FBSDID("$FreeBSD: head/lib/msun/src/e_hypot.c 336362 2018-07-17 07:42:14Z bde $");
 
 /* __ieee754_hypot(x,y)
  *
@@ -70,7 +70,7 @@
 	   if(ha >= 0x7ff00000) {	/* Inf or NaN */
 	       u_int32_t low;
 	       /* Use original arg order iff result is NaN; quieten sNaNs. */
-	       w = fabs(x+0.0)-fabs(y+0.0);
+	       w = fabsl(x+0.0L)-fabs(y+0);
 	       GET_LOW_WORD(low,a);
 	       if(((ha&0xfffff)|low)==0) w = a;
 	       GET_LOW_WORD(low,b);