Fixed "LLVM ERROR: unsupported relocation of variable" when compiling
@Callback methods with debug info. (#566)
IOSTarget will now accept x86_64 as a valid simulator arch. (#553)
Added check for x86_64 in ObjCRuntime.isStret(). Also changed it to throw an
Error for archs we don't explicitly support. (#553)
Fixed alignment of stack in call0 for x86_64. Also cleaned up the stack
alignment code for x86 and added stack alignment calculations to call0 and
proxy0 for Linux x86. (#553)