Fix build on G++ 4.9 on FreeBSD-11.

make-bsd.mk

@@ -52,7 +52,7 @@ ifeq ($(CC_MACH),aarch64)
 endif
 DEFS+=-DZT_BUILD_PLATFORM=$(ZT_BUILD_PLATFORM) -DZT_BUILD_ARCHITECTURE=$(ZT_ARCHITECTURE) -DZT_SOFTWARE_UPDATE_DEFAULT="\"disable\""
 
-CXXFLAGS+=$(CFLAGS) -fno-rtti -std=c++11
+CXXFLAGS+=$(CFLAGS) -fno-rtti -std=c++11 -D_GLIBCXX_USE_C99 -D_GLIBCXX_USE_C99_MATH -D_GLIBCXX_USE_C99_MATH_TR1
 
 all:	one