Start using libc++ by default

Makefile.osx

@@ -1,8 +1,8 @@
 
 PREFIX		:= /usr/local
-CXX		:= g++
-CC		:= gcc
-ARCHFLAGS	:= 
+CXX		:= clang++ -stdlib=libc++
+CC		:= clang
+ARCHFLAGS	:= -arch i386 -arch x86_64 -mmacosx-version-min=10.7
 OPTFLAGS	:= -DNDEBUG -ffast-math -mfpmath=sse -msse -msse2 -O3 -ftree-vectorize
 
 CXXFLAGS	:= $(ARCHFLAGS) $(OPTFLAGS) -I. -Isrc -Irubberband -I/usr/local/include -DUSE_PTHREADS -DMALLOC_IS_ALIGNED -DHAVE_VDSP -DUSE_SPEEX -DNO_THREAD_CHECKS -DNO_TIMING