[ARM] Add FDPIC relocations definitions

[ARM] Add FDPIC relocations definitions

Add FDPIC relocation definitions in BFD and gas.
Gas rejects them if the --fdpic option was not specified.

2018-04-25  Christophe Lyon  <christophe.lyon@st.com>
	Mickaël Guêné  <mickael.guene@st.com>

	bfd/
	* bfd-in2.c (BFD_RELOC_ARM_GOTFUNCDESC)
	(BFD_RELOC_ARM_GOTOFFFUNCDESC, BFD_RELOC_ARM_FUNCDESC)
	(BFD_RELOC_ARM_FUNCDESC_VALUE): New.
	* elf32-arm.c (elf32_arm_howto_table_2): Add R_ARM_GOTFUNCDESC,
	R_ARM_GOTOFFFUNCDESC, R_ARM_FUNCDESC, R_ARM_FUNCDESC_VALUE.
	(elf32_arm_howto_from_type): Take new members of
	elf32_arm_howto_table_2 into account.
	(elf32_arm_reloc_map): Add BFD_RELOC_ARM_GOTFUNCDESC,
	BFD_RELOC_ARM_GOTOFFFUNCDESC, BFD_RELOC_ARM_FUNCDESC,
	BFD_RELOC_ARM_FUNCDESC_VALUE.
	* reloc.c: Add BFD_RELOC_ARM_GOTFUNCDESC,
	BFD_RELOC_ARM_GOTOFFFUNCDESC, BFD_RELOC_ARM_FUNCDESC,
	BFD_RELOC_ARM_FUNCDESC_VALUE.

	gas/
	* config/tc-arm.c (reloc_names): Add gotfuncdesc, gotofffuncdesc,
	funcdesc.
	(md_apply_fix): Support the new relocations.
	(tc_gen_reloc): Likewise.
	* testsuite/gas/arm/reloc-fdpic.d: New.
	* testsuite/gas/arm/reloc-fdpic.s: New.

	include/
	* elf/arm.h (R_ARM_GOTFUNCDESC, R_ARM_GOTOFFFUNCDESC)
	(R_ARM_FUNCDESC)
	(R_ARM_FUNCDESC_VALUE): Define new relocations.