libcxx on older systems (eg 10.6) test and fixes format

[Ken Cunningham]

Hah, hah. Pre-coffee.

Great start -- Mountain Lion is 10.8 -- and I think that's the last one we need to test for instead of 10.9, if I recall Jeremy's note correctly. 


So with 10.8, here:


# Snow Leopard with cxx_stdlib=libc++ fix
platform darwin { 
	if {{${MINOR} == 6} && {${configure.cxx_stdlib} eq "libc++"}} { 

			#do stuff like configure.ldflags-append    "-lc++" 

	} 
} 


and for 10.8 or lower with libcxx, use this:

# Mountain Lion or older with cxx_stdlib=libc++ fix
platform darwin { 
	if {{${MINOR} <= 8} && {${configure.cxx_stdlib} eq "libc++"}} { 

			#do stuff like configure.ldflags-append    "-lc++" 

	} 
} 



Ken