Undo gmainloop related changes

Revert "Merge pull request #1943 from H3rnand3zzz/gmainloop

This reverts commit 609fde0998, reversing
changes made to 2ec94064ed.

Revert "Merge pull request #1948 from H3rnand3zzz/fix/rl-less-refreshes"

This reverts commit 11762fd2b0, reversing
changes made to 609fde0998.

We have got several issues, that we don't quite see how to solve, with
the merge of the gmainloop PR.

* Slashguard is broken (#1955) (though #1956 could fix that)
* One person reported problems with copy paste selection via mouse
* Some input buffer seems not to be cleared correctly
  It happened that I was debugging profanity used `/connect` and typed
  the password. I then debugged so long that a time out occurred, so
  profanity disconnected. Then it printed "unknown command: $password".

There was something else that I forgot now.

Bottomline is: so far we didn't get it right so we will undo these
changes until someone proposes a working solution.

We got a slight performance increase (apparently noticable when
alt+mouse scrolling) but got too many issues with this change.

src/profanity.h

@@ -44,6 +44,5 @@ void prof_run(char* log_level, char* account_name, char* config_file, char* log_
 void prof_set_quit(void);
 
 extern pthread_mutex_t lock;
-extern GMainLoop* mainloop;
 
 #endif