These macros shall be used if there are other arguments.  Unlike the
old variants, they start with a comma.

This replaces a lot of manual freeze() and unfreeze() call.  Doing it
with RAII is safer and easier.

I did not replace all freeze()/unfreeze() pairs because some callers
unfreeze and re-freeze in the middle of a scope.  Sometimes, adding a
new scope can be added just for such a RAII object.  Refactoring that
can be done later.

Notes:

- Instead of using the global variable `dict_sys`, I decided to pass a
  `dict_sys_t` reference parameter, because I believe it will be
  necessary to eliminate that global variable eventually (in order to
  have a per-catalog instance).  Hard-coding this global variable here
  would generate identical (not better) machine code and would be a
  step in the wrong direction.

- The new macros `SRW_LOCK_ARGS2` and `SRW_LOCK_CALL2` were necessary
  because this is the first time those debug-only parameters are
  forwarded from a function that has more parameters (i.e. the
  dict_sys_t reference).