Create mstreamfp before registering signal handlers

We use mstreamfp in notcurses_stop_minimal(), so we can't
register that function as a fatal signal handler until
we've opened mstreamfp. Move it before the registration.
Eliminates a coredump when we ctrl+c during init.

src/lib/notcurses.c

@@ -49,7 +49,8 @@ int reset_term_attributes(const tinfo* ti, FILE* fp){
 
 // Do the minimum necessary stuff to restore the terminal, then return. This is
 // the end of the line for fatal signal handlers. notcurses_stop() will go on
-// to tear down and account for internal structures.
+// to tear down and account for internal structures. note that we do lots of
+// shit here that is unsafe within a signal handler =[ FIXME.
 static int
 notcurses_stop_minimal(void* vnc){
   notcurses* nc = vnc;
@@ -1085,9 +1086,18 @@ notcurses* notcurses_core_init(const notcurses_options* opts, FILE* outfp){
     free(ret);
     return NULL;
   }
+  // mstreamfp is needed by notcurses_stop_minimal, so this must be done
+  // before registering fatal signal handlers.
+  if((ret->rstate.mstreamfp = open_memstream(&ret->rstate.mstream, &ret->rstate.mstrsize)) == NULL){
+    pthread_mutex_destroy(&ret->pilelock);
+    pthread_mutex_destroy(&ret->statlock);
+    free(ret);
+    return NULL;
+  }
   if(setup_signals(ret, (opts->flags & NCOPTION_NO_QUIT_SIGHANDLERS),
                    (opts->flags & NCOPTION_NO_WINCH_SIGHANDLER),
                    notcurses_stop_minimal)){
+    fclose(ret->rstate.mstreamfp);
     pthread_mutex_destroy(&ret->pilelock);
     pthread_mutex_destroy(&ret->statlock);
     free(ret);
@@ -1100,6 +1110,7 @@ notcurses* notcurses_core_init(const notcurses_options* opts, FILE* outfp){
   if(setupterm(opts->termtype, ret->ttyfd, &termerr) != OK){
     fprintf(stderr, "Terminfo error %d (see terminfo(3ncurses))\n", termerr);
     drop_signals(ret);
+    fclose(ret->rstate.mstreamfp);
     pthread_mutex_destroy(&ret->statlock);
     pthread_mutex_destroy(&ret->pilelock);
     free(ret);
@@ -1139,10 +1150,6 @@ notcurses* notcurses_core_init(const notcurses_options* opts, FILE* outfp){
       goto err;
     }
   }
-  if((ret->rstate.mstreamfp = open_memstream(&ret->rstate.mstream, &ret->rstate.mstrsize)) == NULL){
-    free_plane(ret->stdplane);
-    goto err;
-  }
   const char* smkx = get_escape(&ret->tcache, ESCAPE_SMKX);
   if(smkx && term_emit(smkx, ret->ttyfp, false)){
     free_plane(ret->stdplane);