gold/arm.cc: Output mapping symbol for PLT code

gold/arm.cc: Output mapping symbol for PLT code

Output an ARM state mapping symbol at the start of the PLT. With the
current code objdump will fail to disassemble the PLT that gold
creates.

gold/ChangeLog:

2015-02-11  Will Newton  <will.newton@linaro.org>

	PR gold/13321
	* arm.cc (Target_arm::make_plt_section): Create an ARM
	state mapping symbol at the start of the PLT.