GBE: Support local variable inside kernel function.

GBE: Support local variable inside kernel function.

As Clang treat local variable in similar way like global constant,
(they are treated as Global variable in each own address space)
we refine the previous constant implementation in order to
share same code between local variable and global constant.

We will allocate an address register for each GlobalVariable
(constant or local) through calling newRegister().
In later step, through getRegister() we will get a proper
register derived from the allocated address register.

Signed-off-by: Ruiling Song <ruiling.song@intel.com>
Reviewed-by: "Yang, Rong R" <rong.r.yang@intel.com>