extend.texi: Mark builtin arguments with @var{...}

In many cases we just specify types for the builtin arguments, in other cases
types and names with @var{name} syntax, and in other case with just name.

Shall we tweak that somehow?  If the argument names are unimportant, perhaps
it is fine to leave that out, but shouldn't we always use @var{...} around
the parameter names when specified?

On Fri, Dec 01, 2023 at 10:43:57AM -0700, Sandra Loosemore wrote:
> Yup.  The Texinfo manual says:  "When using @deftypefn command and
> variations, you should mark parameter names with @var to distinguish these
> from data type names, keywords, and other parts of the literal syntax of the
> programming language."

Here is a patch which does that (but not adding types to where they were
missing, that will be harder to search for).

2023-12-11  Jakub Jelinek  <jakub@redhat.com>

	* doc/extend.texi (__sync_fetch_and_add, __sync_fetch_and_sub,
	__sync_fetch_and_or, __sync_fetch_and_and, __sync_fetch_and_xor,
	__sync_fetch_and_nand, __sync_add_and_fetch, __sync_sub_and_fetch,
	__sync_or_and_fetch, __sync_and_and_fetch, __sync_xor_and_fetch,
	__sync_nand_and_fetch, __sync_bool_compare_and_swap,
	__sync_val_compare_and_swap, __sync_lock_test_and_set,
	__sync_lock_release, __atomic_load_n, __atomic_load, __atomic_store_n,
	__atomic_store, __atomic_exchange_n, __atomic_exchange,
	__atomic_compare_exchange_n, __atomic_compare_exchange,
	__atomic_add_fetch, __atomic_sub_fetch, __atomic_and_fetch,
	__atomic_xor_fetch, __atomic_or_fetch, __atomic_nand_fetch,
	__atomic_fetch_add, __atomic_fetch_sub, __atomic_fetch_and,
	__atomic_fetch_xor, __atomic_fetch_or, __atomic_fetch_nand,
	__atomic_test_and_set, __atomic_clear, __atomic_thread_fence,
	__atomic_signal_fence, __atomic_always_lock_free,
	__atomic_is_lock_free, __builtin_add_overflow,
	__builtin_sadd_overflow, __builtin_saddl_overflow,
	__builtin_saddll_overflow, __builtin_uadd_overflow,
	__builtin_uaddl_overflow, __builtin_uaddll_overflow,
	__builtin_sub_overflow, __builtin_ssub_overflow,
	__builtin_ssubl_overflow, __builtin_ssubll_overflow,
	__builtin_usub_overflow, __builtin_usubl_overflow,
	__builtin_usubll_overflow, __builtin_mul_overflow,
	__builtin_smul_overflow, __builtin_smull_overflow,
	__builtin_smulll_overflow, __builtin_umul_overflow,
	__builtin_umull_overflow, __builtin_umulll_overflow,
	__builtin_add_overflow_p, __builtin_sub_overflow_p,
	__builtin_mul_overflow_p, __builtin_addc, __builtin_addcl,
	__builtin_addcll, __builtin_subc, __builtin_subcl, __builtin_subcll,
	__builtin_alloca, __builtin_alloca_with_align,
	__builtin_alloca_with_align_and_max, __builtin_speculation_safe_value,
	__builtin_nan, __builtin_nand32, __builtin_nand64, __builtin_nand128,
	__builtin_nanf, __builtin_nanl, __builtin_nanf@var{n},
	__builtin_nanf@var{n}x, __builtin_nans, __builtin_nansd32,
	__builtin_nansd64, __builtin_nansd128, __builtin_nansf,
	__builtin_nansl, __builtin_nansf@var{n}, __builtin_nansf@var{n}x,
	__builtin_ffs, __builtin_clz, __builtin_ctz, __builtin_clrsb,
	__builtin_popcount, __builtin_parity, __builtin_bswap16,
	__builtin_bswap32, __builtin_bswap64, __builtin_bswap128,
	__builtin_extend_pointer, __builtin_goacc_parlevel_id,
	__builtin_goacc_parlevel_size, vec_clrl, vec_clrr, vec_mulh, vec_mul,
	vec_div, vec_dive, vec_mod, __builtin_rx_mvtc): Use @var{...} around
	parameter names.
	(vec_rl, vec_sl, vec_sr, vec_sra): Likewise.  Use @var{...} also
	around A, B and R in description.