xram - stub routines for setting up external memory

This is a stub project designed to demonstrate how to initialize the 64K address space of the MAVRIC-II-RE module, or the external memory chip on the MAVRIC-IB board. The needed codes consists of an initialization routine to be execuded by the GCC runtime early in its startup sequence, as well as passing options to the linker from the Makefile so that the linker knows how to place variables an initialize the stack.