[PATCH, rs6000] Correct descriptions of __builtin_bcdadd* and _builtin_bcdsub* functions

[Kelvin Nilsen]

Several errors were discovered in the descriptions of the __builtin_bcdadd, 
__builtin_bcdadd_lt, __builtin_bcdadd_eq,         __builtin_bcdadd_gt, 
__builtin_bcdadd_ov, __builtin_bcdsub, __builtin_bcdsub_lt, 
__builtin_bcdsub_eq, __builtin_bcdsub_gt, and __builtin_bcdsub_ov functions.  
This patch corrects these documentation errors.

I have built the gcc.pdf file and reviewed the formatting, and all looks good.

Is this ok for trunk?

gcc/ChangeLog:

2018-08-01  Kelvin Nilsen  <kel...@gcc.gnu.org>

        * doc/extend.texi (PowerPC AltiVec Built-in Functions Available on
        ISA 2.07): Correct spelling of bcdsub to be __builtin_bcdsub.  Add
        third argument of type "const signed char" to descriptions of
        __builtin_bcdadd, __builtin_bcdadd_lt, __builtin_bcdadd_eq,
        __builtin_bcdadd_gt, __builtin_bcdadd_ov, __builtin_bcdsub,
        __builtin_bcdsub_lt, __builtin_bcdsub_eq, __builtin_bcdsub_gt,
        __builtin_bcdsub_ov functions.

Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi (revision 263068)
+++ gcc/doc/extend.texi (working copy)
@@ -18383,16 +18383,16 @@ vector __uint128 vec_vsubcuq (vector __uint128, ve
 __int128 vec_vsubuqm (__int128, __int128);
 __uint128 vec_vsubuqm (__uint128, __uint128);
 
-vector __int128 __builtin_bcdadd (vector __int128, vector __int128);
-int __builtin_bcdadd_lt (vector __int128, vector __int128);
-int __builtin_bcdadd_eq (vector __int128, vector __int128);
-int __builtin_bcdadd_gt (vector __int128, vector __int128);
-int __builtin_bcdadd_ov (vector __int128, vector __int128);
-vector __int128 bcdsub (vector __int128, vector __int128);
-int __builtin_bcdsub_lt (vector __int128, vector __int128);
-int __builtin_bcdsub_eq (vector __int128, vector __int128);
-int __builtin_bcdsub_gt (vector __int128, vector __int128);
-int __builtin_bcdsub_ov (vector __int128, vector __int128);
+vector __int128 __builtin_bcdadd (vector __int128, vector __int128, const 
signed char);
+int __builtin_bcdadd_lt (vector __int128, vector __int128, const signed char);
+int __builtin_bcdadd_eq (vector __int128, vector __int128, const signed char);
+int __builtin_bcdadd_gt (vector __int128, vector __int128, const signed char);
+int __builtin_bcdadd_ov (vector __int128, vector __int128, const signed char);
+vector __int128 __builtin_bcdsub (vector __int128, vector __int128, const 
signed char);
+int __builtin_bcdsub_lt (vector __int128, vector __int128, const signed char);
+int __builtin_bcdsub_eq (vector __int128, vector __int128, const signed char);
+int __builtin_bcdsub_gt (vector __int128, vector __int128, const signed char);
+int __builtin_bcdsub_ov (vector __int128, vector __int128, const signed char);
 @end smallexample
 
 @node PowerPC AltiVec Built-in Functions Available on ISA 3.0