gdb: Use add_setshow_zuinteger_unlimited_cmd in remote.c

Switch to use add_setshow_zuinteger_unlimited_cmd for some of the
control variables in remote.c.  The variables
hardware-watchpoint-limit, hardware-breakpoint-limit, and
hardware-watchpoint-length-limit are all changed.  For example, a user
will now see this:

    (gdb) show remote hardware-breakpoint-limit
    The maximum number of target hardware breakpoints is unlimited.

Instead of this:

    (gdb) show remote hardware-breakpoint-limit
    The maximum number of target hardware breakpoints is -1.

And can do this:

    (gdb) set remote hardware-breakpoint-limit unlimited

However, previously any negative value implied "unlimited", now only
-1, or the text "unlimited" can be used for unlimited.  Any other
negative value will give an error about invalid input.  This is a
small change in the user interface, but, hopefully, this will not
cause too many problems.

I've also added show functions for these three variables to allow for
internationalisation.

gdb/ChangeLog:

	* remote.c (show_hardware_watchpoint_limit): New function.
	(show_hardware_watchpoint_length_limit): New function.
	(show_hardware_breakpoint_limit): New function.
	(_initialize_remote): Use add_setshow_zuinteger_unlimited_cmd
	where appropriate, update help text.

gdb/doc/ChangeLog:

	* gdb.texinfo (Remote Configuration): Update descriptions for
	set/show of hardware-watchpoint-limit, hardware-breakpoint-limit,
	and hardware-watchpoint-length-limit variables.

2 files changed, 19 insertions, 5 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index fbdab9b..adb97a5 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,9 @@
+2018-07-09  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* gdb.texinfo (Remote Configuration): Update descriptions for
+	set/show of hardware-watchpoint-limit, hardware-breakpoint-limit,
+	and hardware-watchpoint-length-limit variables.
+
 2018-07-02  Maciej W. Rozycki  <macro@mips.com>
 
 	PR tdep/8282
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 91ec219..245d3f1 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -21161,16 +21161,24 @@ responses.
 @anchor{set remote hardware-breakpoint-limit}
 @item set remote hardware-watchpoint-limit @var{limit}
 @itemx set remote hardware-breakpoint-limit @var{limit}
-Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
-watchpoints.  A limit of -1, the default, is treated as unlimited.
+Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
+or breakpoints.  The @var{limit} can be set to 0 to disable hardware
+watchpoints or breakpoints, and @code{unlimited} for unlimited
+watchpoints or breakpoints.
+
+@item show remote hardware-watchpoint-limit
+@itemx show remote hardware-breakpoint-limit
+Show the current limit for the number of hardware watchpoints or
+breakpoints that @value{GDBN} can use.
 
 @cindex limit hardware watchpoints length
 @cindex remote target, limit watchpoints length
 @anchor{set remote hardware-watchpoint-length-limit}
 @item set remote hardware-watchpoint-length-limit @var{limit}
-Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
-a remote hardware watchpoint.  A limit of -1, the default, is treated
-as unlimited.
+Restrict @value{GDBN} to using @var{limit} bytes for the maximum
+length of a remote hardware watchpoint.  A @var{limit} of 0 disables
+hardware watchpoints and @code{unlimited} allows watchpoints of any
+length.
 
 @item show remote hardware-watchpoint-length-limit
 Show the current limit (in bytes) of the maximum length of