Update Xcode checks for 10.8

Library/Homebrew/cmd/doctor.rb

@@ -240,6 +240,7 @@ def check_for_latest_xcode
     when 10.5 then "3.1.4"
     when 10.6 then "3.2.6"
     when 10.7 then "4.3.3"
+    when 10.8 then "4.4"
     else nil
   end
   if latest_xcode.nil?

Library/Homebrew/macos.rb

@@ -270,8 +270,10 @@ module MacOS extend self
           "4.2"
         when 31
           "4.3"
+        when 40
+          "4.4"
         else
-          "4.3"
+          "4.4"
         end
       end
     end
@@ -399,7 +401,8 @@ module MacOS extend self
     "4.3" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318},
     "4.3.1" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318},
     "4.3.2" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318},
-    "4.3.3" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318}
+    "4.3.3" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318},
+    "4.4" => {:llvm_build_version=>2336, :clang_version=>"4.0", :clang_build_version=>421}
   }
 
   def compilers_standard?