Refine the 'watchpoint set' command to now require either the '-v' option (for...

Refine the 'watchpoint set' command to now require either the '-v' option (for watching of a variable) or
the '-e' option (for watching of an address) to be present.

Update some existing test cases with the required option and add some more test cases.

Since the '-v' option takes <variable-name> and the '-e' option takes <expr> as the command arg,
the existing infrastructure for generating the option usage can produce confusing help message,
like:

  watchpoint set -e [-w <watch-type>] [-x <byte-size>] <variable-name | expr>
  watchpoint set -v [-w <watch-type>] [-x <byte-size>] <variable-name | expr>

The solution adopted is to provide an extra member field to the struct CommandArgumentData called
(uint32_t)arg_opt_set_association, whose purpose is to link this particular argument data with some
option set(s).  Also modify the signature of CommandObject::GetFormattedCommandArguments() to:

  GetFormattedCommandArguments (Stream &str, uint32_t opt_set_mask = LLDB_OPT_SET_ALL)

it now takes an additional opt_set_mask which can be used to generate a filtered formatted command
args for help message.

Options::GenerateOptionUsage() impl is modified to call the GetFormattedCommandArguments() appropriately.
So that the help message now looks like:

  watchpoint set -e [-w <watch-type>] [-x <byte-size>] <expr>
  watchpoint set -v [-w <watch-type>] [-x <byte-size>] <variable-name>

rdar://problem/10703256

llvm-svn: 150032