fix where `rake retina=3.5' does not work with Xcode 5 DP-2
rake build now honors the 'keep_temps' env variable, if set, llvm bitcode and asm files will not be deleted from the build directory
fix a bug where `rake' command would re-launch an iOS 7 simulator every time

iOS 7 has only retina simulator and com.apple.iphonesimulator indicates "iPhone Retina (4-inch)" as default.
So, we need to use retina even if it does not configure ENV['retina']
fix where it does not generate 64bit type into brigesupport in 3rd-party library on MacOSX platform

http://hipbyte.myjetbrains.com/youtrack/issue/RM-192