Added better support for darwinport's version of FFTW

dtool/Config.pp

@@ -475,7 +475,9 @@
 #define FFTW_LPATH /usr/local/lib
 #define FFTW_LIBS rfftw fftw
 #defer HAVE_FFTW $[libtest $[FFTW_LPATH],$[FFTW_LIBS]]
-
+// This is because darwinport's version of the fftw lib is called
+// drfftw instead of rfftw.
+#defer HAVE_DRFFTW_H $[libtest $[FFTW_LPATH],drfftw]
 
 // Is Berkeley DB installed, and where?  Presently, this is only used
 // for some applications (egg-optchar in particular) in Pandatool, and

dtool/LocalSetup.pp

@@ -506,6 +506,9 @@ $[cdefine HAVE_GLOB_H]
 /* Define if you have the <dirent.h> header file.  */
 $[cdefine HAVE_DIRENT_H]
 
+/* Define if you have the <drfftw.h> header file.  */
+$[cdefine HAVE_DRFFTW_H]
+
 /* Do we have <sys/soundcard.h> (and presumably a Linux-style audio
    interface)? */
 $[cdefine HAVE_SYS_SOUNDCARD_H]