gdb: remove reggroup_next and reggroup_prev

Add a new function gdbarch_reggroups that returns a reference to a
vector containing all the reggroups for an architecture.

Make use of this function throughout GDB instead of the existing
reggroup_next and reggroup_prev functions.

Finally, delete the reggroup_next and reggroup_prev functions.

Most of these changes are pretty straight forward, using range based
for loops instead of the old style look using reggroup_next.  There
are two places where the changes are less straight forward.

In gdb/python/py-registers.c, the register group iterator needed to
change slightly.  As the iterator is tightly coupled to the gdbarch, I
just fetch the register group vector from the gdbarch when needed, and
use an index counter to find the next item from the vector when
needed.

In gdb/tui/tui-regs.c the tui_reg_next and tui_reg_prev functions are
just wrappers around reggroup_next and reggroup_prev respectively.
I've just inlined the logic of the old functions into the tui
functions.  As the tui function had its own special twist (wrap around
behaviour) I think this is OK.

There should be no user visible changes after this commit.

1 files changed, 7 insertions, 7 deletions

diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index b76345d..9abb91f 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -2295,17 +2295,17 @@ registers_info (const char *addr_exp, int fpregs)
 
       /* A register group?  */
       {
-	struct reggroup *group;
-
-	for (group = reggroup_next (gdbarch, NULL);
-	     group != NULL;
-	     group = reggroup_next (gdbarch, group))
+	const struct reggroup *group = nullptr;
+	for (const struct reggroup *g : gdbarch_reggroups (gdbarch))
 	  {
 	    /* Don't bother with a length check.  Should the user
 	       enter a short register group name, go with the first
 	       group that matches.  */
-	    if (strncmp (start, reggroup_name (group), end - start) == 0)
-	      break;
+	    if (strncmp (start, reggroup_name (g), end - start) == 0)
+	      {
+		group = g;
+		break;
+	      }
 	  }
 	if (group != NULL)
 	  {