i386: Rename to ix86_indirect_branch_register

i386: Rename to ix86_indirect_branch_register

Rename the variable for -mindirect-branch-register to
ix86_indirect_branch_register to match the command-line option name.

	* config/i386/constraints.md (Bs): Replace
	ix86_indirect_branch_thunk_register with
	ix86_indirect_branch_register.
	(Bw): Likewise.
	* config/i386/i386.md (indirect_jump): Likewise.
	(tablejump): Likewise.
	(*sibcall_memory): Likewise.
	(*sibcall_value_memory): Likewise.
	Peepholes of indirect call and jump via memory: Likewise.
	* config/i386/i386.opt: Likewise.
	* config/i386/predicates.md (indirect_branch_operand): Likewise.
	(GOT_memory_operand): Likewise.
	(call_insn_operand): Likewise.
	(sibcall_insn_operand): Likewise.
	(GOT32_symbol_operand): Likewise.

From-SVN: r256712