Added a flag to the Mac info.plist which allows high-dpi windows to be created in all situations when requested and supported.

platform/xcode/macosx/love-macosx.plist

@@ -63,6 +63,8 @@
 	<string>LoVe</string>
 	<key>LSApplicationCategoryType</key>
 	<string>public.app-category.games</string>
+	<key>NSHighResolutionCapable</key>
+	<true/>
 	<key>NSHumanReadableCopyright</key>
 	<string>© 2006-2015 LÖVE Development Team</string>
 	<key>NSPrincipalClass</key>