Remove pragmas

No functional changes.  I learned a little trick that allows us to remove the -Wunused-parameter warning suppression pragmas from our code.  (Well it's not really a trick... it's from the first item in Herb Sutter's famous C++ Coding Standards.)

Also, define the listen label in CListener only conditionally, so we can get rid of our only other use of pragmas.  Now that we're clean, the challenge is to remain drug free.