Support AMD64/Intel ISAs in assembler/disassembler

Support AMD64/Intel ISAs in assembler/disassembler

AMD64 spec and Intel64 spec differ in direct unconditional branches in
64-bit mode.  AMD64 supports direct unconditional branches with 16-bit
offset via the data size prefix, which truncates RIP to 16 bits, while
the data size prefix is ignored by Intel64.

This patch adds -mamd64/-mintel64 option to x86-64 assembler and
-Mamd64/-Mintel64 option to x86-64 disassembler.  The most permissive
ISA, which is AMD64, is the default.

GDB can add an option, similar to

(gdb) help set disassembly-flavor
Set the disassembly flavor.
The valid values are "att" and "intel", and the default value is "att".

to select which ISA to disassemble.

binutils/

	PR binutis/18386
	* doc/binutils.texi: Document -Mamd64 and -Mintel64.

gas/

	PR binutis/18386
	* config/tc-i386.c (OPTION_MAMD64): New.
	(OPTION_MINTEL64): Likewise.
	(md_longopts): Add -mamd64 and -mintel64.
	(md_parse_option): Handle OPTION_MAMD64 and OPTION_MINTEL64.
	(md_show_usage): Add -mamd64 and -mintel64.
	* doc/c-i386.texi: Document -mamd64 and -mintel64.

gas/testsuite/

	PR binutis/18386
	* gas/i386/i386.exp: Run x86-64-branch-2 and x86-64-branch-3.
	* gas/i386/x86-64-branch.d: Also pass -Mintel64 to objdump.
	* gas/i386/ilp32/x86-64-branch.d: Likewise.
	* gas/i386/x86-64-branch-2.d: New file.
	* gas/i386/x86-64-branch-2.s: Likewise.
	* gas/i386/x86-64-branch-3.l: Likewise.
	* gas/i386/x86-64-branch-3.s: Likewise.

ld/testsuite/

	PR binutis/18386
	* ld-x86-64/tlsgdesc.dd: Also pass -Mintel64 to objdump.
	* ld-x86-64/tlspic.dd: Likewise.
	* ld-x86-64/x86-64.exp (x86_64tests): Also pass -Mintel64 to
	objdump for tlspic.dd and tlsgdesc.dd.

opcodes/

	PR binutis/18386
	* i386-dis.c: Add comments for '@'.
	(x86_64_table): Use '@' on call/jmp for X86_64_E8/X86_64_E9.
	(enum x86_64_isa): New.
	(isa64): Likewise.
	(print_i386_disassembler_options): Add amd64 and intel64.
	(print_insn): Handle amd64 and intel64.
	(putop): Handle '@'.
	(OP_J): Don't ignore the operand size prefix for AMD64 in 64-bit.
	* i386-gen.c (cpu_flags): Add CpuAMD64 and CpuIntel64.
	* i386-opc.h (AMD64): New.
	(CpuIntel64): Likewise.
	(i386_cpu_flags): Add cpuamd64 and cpuintel64.
	* i386-opc.tbl: Add direct call/jmp with Disp16|Disp32 for AMD64.
	Mark direct call/jmp without Disp16|Disp32 as Intel64.
	* i386-init.h: Regenerated.
	* i386-tbl.h: Likewise.