Add get_constant_ptr method to kernel instance which is used for getting the address of a constant in a jit kernel.  When the ptx string is created, a map is created which is a map from the demangled name onto the mangled name used in the ptx/
Add get_constant_ptr method to kernel instance which is used for getting the address of a constant in a jit kernel.  When the ptx string is created, a map is created which is a map from the demangled name onto the mangled name used in the ptx/

NVIDIA/jitify,NVIDIA/jitify