Add string test for string interpolation

fixed prototype warning (-Wstrict-prototypes)

fixed prototype: g++ will complain about definition not being a prototype, should work with GCC and VC as well

fixed prototype: g++ will complain about definition not being a prototype, should work with GCC and VC as well

fixed const_get && const_missing issue

Could you add me to AUTHORS?

'mrb_sym' used as 'uint32_t'. it's broken portability; based on the work from @crimsonwoods; close #216

Add Test Case for issue #211

Add Test Case for issue #210

enhance CMake support for Xcode native builds

use mrb_malloc instead of malloc

Use "if" instead "switch".

Similar to the existing CMake Visual Studio IDE support, allow CMake to
generate Xcode project files in mruby's root directory. This enables
workflows normally expected by Xcode IDE users.