Use is_32_bit? and remove negatives.

Formula/ffmpeg.rb

@@ -38,7 +38,7 @@ class Ffmpeg <Formula
 
     # For 32-bit compilation under gcc 4.2, see:
     # http://trac.macports.org/ticket/20938#comment:22
-    if MACOS_VERSION >= 10.6 and not Hardware.is_64_bit?
+    if MACOS_VERSION >= 10.6 and Hardware.is_32_bit?
       ENV.append_to_cflags "-mdynamic-no-pic"
     end
 

Formula/p7zip.rb

@@ -10,7 +10,7 @@ class P7zip <Formula
   end
 
   def build_32bit?
-    ARGV.include? '--32-bit' or !Hardware.is_64_bit?
+    ARGV.include? '--32-bit' or Hardware.is_32_bit?
   end
 
   def install

Formula/pbrt.rb

@@ -27,7 +27,7 @@ class Pbrt <Formula
       contents.change_make_var! "EXR_LIBDIR", "-L#{openexr.lib} -L#{ilmbase.lib}"
 
       # Change settings if we are using a 32bit system
-      if MACOS_VERSION <= 10.5 or not Hardware.is_64_bit?
+      if MACOS_VERSION <= 10.5 or Hardware.is_32_bit?
         contents.change_make_var! "MARCH", "-m32 -msse2 -mfpmath=sse"
       end
     end