Introduce gfp_mask variants of _stp allocation functions.

Introduce gfp_mask variants of _stp allocation functions.

* runtime/alloc.c: Add _stp_kmalloc_gfp(), _stp_kzalloc_gfp() and
  _stp_kmalloc_node_gfp() which take a gfp_mask in case you really know
  what you are doing.
* translate.cxx (emit_module_init): Use with GFP_KERNEL for context alloc.
* runtime/map.c: Use for init and new functions called at module_init time.
* runtime/stat.c: Likewise.