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, 1 insertions, 5 deletions

diff --git a/gdb/completer.c b/gdb/completer.c
index 63b4cd22d24..f4b5917095d 100644
--- a/gdb/completer.c
+++ b/gdb/completer.c
@@ -1819,11 +1819,7 @@ reg_or_group_completer_1 (completion_tracker &tracker,
 
   if ((targets & complete_reggroup_names) != 0)
     {
-      struct reggroup *group;
-
-      for (group = reggroup_next (gdbarch, NULL);
-	   group != NULL;
-	   group = reggroup_next (gdbarch, group))
+      for (const struct reggroup *group : gdbarch_reggroups (gdbarch))
 	{
 	  name = reggroup_name (group);
 	  if (strncmp (word, name, len) == 0)