stop using Mac specific compiler option "Wno-long-double"

having this option results in a warning for each compile on gcc>=4.2 or clang.
Apple says in http://lists.cs.uiuc.edu/pipermail/llvmdev/2008-June/015095.html
"[...] the best thing is not to use it. There is no reason to."

solenv/gbuild/platform/macosx.mk

@@ -90,7 +90,6 @@ gb_CXXFLAGS := \
 	-Wendif-labels \
 	-Wextra \
 	-Wno-ctor-dtor-privacy \
-	-Wno-long-double \
 	-Wno-non-virtual-dtor \
 	-fPIC \
 	-fmessage-length=0 \

solenv/inc/unxmacx.mk

@@ -111,7 +111,7 @@ CFLAGSEXCEPTIONS=-fexceptions -fno-enforce-eh-specs
 CFLAGS_NO_EXCEPTIONS=-fno-exceptions
 
 # Normal C++ compilation flags
-CFLAGSCXX=-pipe -malign-natural -fsigned-char -Wno-long-double $(ARCH_FLAGS)
+CFLAGSCXX=-pipe -malign-natural -fsigned-char $(ARCH_FLAGS)
 CFLAGSCXX+= -Wno-ctor-dtor-privacy
 
 PICSWITCH:=-fPIC