[CM] compiling snd 15.7 on osx 10.10

[Bill Schottstaedt]

Find IntrinsicP.h (via locate or maybe the Finder), then include the
path to it in the CFLAGS variable -- it's probably in something
like /sw/X11/include/X11.  The old (very old!) configure script
made heroic efforts to find the X headers, but I removed all
that stuff when we tried to move to premake.  I think all 
references to IntrinsicP.h in Snd include the (inner) X11, so you'd 
use -I/sw/X11/include.