Fix arm process record for some instructions

Fix arm process record for some instructions

I look at some fails in gdb.reverse/solib-precsave.exp in -mthumb,
they are caused by some bugs on decoding these three instructions,
uxtb, ldr and mrc.  This patch adds unit tests against these three
instructions, and fix these bugs by re-organizing the code to match
the table in ARM ARM.

gdb:

2017-03-16  Yao Qi  <yao.qi@linaro.org>

	* arm-tdep.c [GDB_SELF_TEST]: include "selftests.h".
	(arm_record_test): Declare.
	(_initialize_arm_tdep) [GDB_SELF_TEST]: call register_self_test.
	(thumb_record_ld_st_reg_offset): Rewrite the opcode matching to
	align with the manual.
	(thumb_record_misc): Adjust the code order to align with the
	manual.
	(thumb2_record_decode_insn_handler): Fix instruction matching.
	(instruction_reader_thumb): New class.
	(arm_record_test): New function.