This patch adds a default-collect variable that is a list of expressions 
that every tracepoint should collect.  It is a minor convenience in that 
it is entirely equivalent to a first collect action attached to every 
tracepoint; but in a multiple-tracepoint scenario, it is frequently 
useful to know that registers are always available, or that a global 
timestamp was always collected.  It is also handy to be able to affect 
every tracepoint's action list just by changing this variable.

As with other changes in this area, it has been mostly tested with our 
inhouse target agent; full FSF testsuite will need the queued-up 
gdbserver patches for tracepoints.

Stan

2009-12-29  Stan Shebs  <stan@codesourcery.com>

    Add default-collect variable.
    * tracepoint.c (default_collect): New global.
    (encode_actions): Use it.
    (download_tracepoint): Test it, for otherwise
    action-less tracepoints.
    (_initialize_tracepoint): Add set/show.
    * NEWS: Mention default-collect.

    * gdb.texinfo (Tracepoint Actions): Describe default-collect.
   
    * gdb.trace/actions.exp: Test default-collect.