Adds code to the MSP430 linker to transform a 4-byte BR instruction into

Adds code to the MSP430 linker to transform a 4-byte BR instruction into
a 2-byte JMP instruction, when this can be done safely.

	* elf32-msp430.c (msp430_elf_relax_section): Add relaxation of
	16-bit absolute BR instructions to 10-bit pc-relative JMP
	instructions.