Add createLocalVariableDefinitions

This function is used to create GPU local variables, i.e. for shared
memory array or private memory definitions.
 + Add static function getLLVMTypeByName - use this function to get
   the llvm::Type of a type string. (This is a ugly and temporary
   solution.)
Add createKernelCopy function

This function is use to create LLVM IR for copy statement in a kernel
when shared memory or private memory code generation is enabled.
Add ArryIDs to store maps of array name to its isl_id.
Replace kernel_*_stmt's base with shared memory address.

In case shared memory code generation is used, set map of an array id
in IDToValue to its corresponding shared memory address so that we can
create a correct share memory load/store.
Add eraseSharedMemoryBases

This function is used to erase all the allocated shared memory from the
host module after the complete of the GPGPU code generation.