Fix build for Xcode 7 or earlier

Author: splhack

src/MacVim/DBPrefsWindowController.m

@@ -2,6 +2,7 @@
 //  DBPrefsWindowController.m
 //
 
+#import "MacVim.h"
 #import "DBPrefsWindowController.h"
 
 

src/MacVim/MMApplication.m

@@ -13,6 +13,7 @@
  * Some default NSApplication key input behavior is overridden here.
  */
 
+#import "MacVim.h"
 #import "MMApplication.h"
 
 @implementation MMApplication

src/MacVim/MMCoreTextView+ToolTip.m

@@ -19,6 +19,7 @@
  * changes were made to adapt the code to MacVim.
  */
 
+#import "MacVim.h"
 #import "MMCoreTextView.h"