btf: Add support to BTF_KIND_ENUM64 type

btf: Add support to BTF_KIND_ENUM64 type

BTF supports 64-bits enumerators with following encoding:

  struct btf_type:
    name_off: 0 or offset to a valid C identifier
    info.kind_flag: 0 for unsigned, 1 for signed
    info.kind: BTF_KIND_ENUM64
    info.vlen: number of enum values
    size: 1/2/4/8

The btf_type is followed by info.vlen number of:

    struct btf_enum64
    {
      uint32_t name_off;   /* Offset in string section of enumerator name.  */
      uint32_t val_lo32;   /* lower 32-bit value for a 64-bit value Enumerator */
      uint32_t val_hi32;   /* high 32-bit value for a 64-bit value Enumerator */
    };

So, a new btf_enum64 structure was added to represent BTF_KIND_ENUM64
and a new field dtd_enum_unsigned in ctf_dtdef structure to distinguish
when CTF enum is a signed or unsigned type, later that information is
used to encode the BTF enum type.

gcc/ChangeLog:

	* btfout.cc (btf_calc_num_vbytes): Compute enumeration size depending of
	enumerator type btf_enum{,64}.
	(btf_asm_type): Update btf_kflag according to enumeration type sign
	using dtd_enum_unsigned field for both:  BTF_KIND_ENUM{,64}.
	(btf_asm_enum_const): New argument to represent the size of
	the BTF enum type, writing the enumerator constant value for
	32 bits, if it's 64 bits then explicitly writes lower 32-bits
	value and higher 32-bits value.
	(output_asm_btf_enum_list): Add enumeration size argument.
	* ctfc.cc (ctf_add_enum): New argument to represent CTF enum
	basic information.
	(ctf_add_generic): Use of ei_{name. size, unsigned} to build the
	dtd structure containing enumeration information.
	(ctf_add_enumerator): Update comment mention support for BTF
	enumeration in 64-bits.
	* dwarf2ctf.cc (gen_ctf_enumeration_type): Extract signedness
	for enumeration type and use it in ctf_add_enum.
	* ctfc.h (ctf_dmdef): Update dmd_value to HOST_WIDE_INT to allow
	use 32/64 bits enumerators.
	information.
	(ctf_dtdef): New field to describe enum signedness.

include/
	* btf.h (btf_enum64): Add new definition and new symbolic
	constant to BTF_KIND_ENUM64 and BTF_KF_ENUM_{UN,}SIGNED.

gcc/testsuite/ChangeLog:

	* gcc.dg/debug/btf/btf-enum-1.c: Update testcase, with correct
	info.kflags encoding.
	* gcc.dg/debug/btf/btf-enum64-1.c: New testcase.