add @kindex for catchpoints

add @kindex for catchpoints

I wanted to find the docs for "catch load" the other day, and I found
out that this isn't in the index.  It seems to me that each command
ought to be in the index for quick reference like this, so this patch
adds an @kindex (chosen because it seems to be what the rest of the
manual does) for each "catch" subcommand.

2013-12-03  Tom Tromey  <tromey@redhat.com>

	* gdb.texinfo (Set Catchpoints): Add @kindex for each command
	documented here.