Move BLUR_TRANSPARENCY into its own file

... so that both Vim and MacVim can see it.

I'm an idiot and didn't realize MacVim doesn't reference vim.h, so of
course the #define can't be there.

src/MacVim/MMVimController.m

@@ -35,6 +35,7 @@
 #import "Miscellaneous.h"
 #import "MMCoreTextView.h"
 #import "MMWindow.h"
+#import "blur.h"
 
 
 static NSString *MMDefaultToolbarImageName = @"Attention";

src/MacVim/MMWindow.h

@@ -9,6 +9,7 @@
  */
 
 #import "MacVim.h"
+#import "blur.h"
 
 
 

src/MacVim/MMWindowController.h

@@ -9,6 +9,7 @@
  */
 
 #import "MacVim.h"
+#import "blur.h"
 
 
 

src/MacVim/blur.h

@@ -0,0 +1,3 @@
+#if defined(MAC_OS_X_VERSION_10_5) && (MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_5)
+# define BLUR_TRANSPARENCY
+#endif

src/vim.h

@@ -1752,8 +1752,8 @@ typedef int proftime_T;	    /* dummy for function prototypes */
 #endif
 
 /* Needs to be before option.h, which uses BLUR_TRANSPARENCY */
-#if defined(FEAT_TRANSPARENCY) && defined(MAC_OS_X_VERSION_10_5) && (MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_5)
-# define BLUR_TRANSPARENCY
+#ifdef FEAT_TRANSPARENCY
+# include "MacVim/blur.h"
 #endif
 
 /* Include option.h before structs.h, because the number of window-local and