arm: move the switch tables for Arm to the RO data section.

arm: move the switch tables for Arm to the RO data section.

Follow up patch to arm: Use deltas for Arm switch tables
This patch moves the switch tables for Arm from the .text section
into the .rodata section.

gcc/ChangeLog:

	* config/arm/aout.h: Change to use the Lrtx label.
	* config/arm/arm.h (CASE_VECTOR_PC_RELATIVE): Remove arm targets
	from (!target_pure_code) condition.
	(ADDR_VEC_ALIGN): Add align for tables in rodata section.
	* config/arm/arm.cc (arm_output_casesi): Alter the function to include
	.Lrtx label and remove adr instructions.
	* config/arm/arm.md
	(arm_casesi_internal): Use force_reg to generate ldr instructions that
	would otherwise be out of range, and change rtl to accommodate force reg.
	Additionally remove unnecessary register temp.
	(casesi): Remove pure code check for Arm.
	* config/arm/elf.h (JUMP_TABLES_IN_TEXT_SECTION): Remove arm
	targets from JUMP_TABLES_IN_TEXT_SECTION definition.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/arm-switchstatement.c: Alter the tests to
	change adr instruction to ldr.