Fix 324514  gdbserver monitor cmd output behaviour consistency + allow user
            to put a "marker" msg in process log output

* v.info n_errs_found accepts optional msg, added in the output of
   the monitor command.

* use VG_(printf) rather than VG_(gdb_printf) when output of command
  should be redirected according to v.set gdb_output|log_output|mixed_output

* also avoid calling gdb_printf in output sink processing
  to output zero bytes, as gdb_printf expects to have a null terminated
  string, which is not ensured when 0 bytes have to be output.

* some minor reformatting (replace char* xxx by char *xxx).




git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13532 a5019735-40e9-0310-863c-91ae7b9d1cf9