Fixed|Console|All Games: Don't begin a game state change message if waiting for a response

This is possible if the user tries to circumvent the message response
prompt by opening the console and entering a command that triggers a
new message.

Todo: These game state messages should be considered modal - opening
of the console should be prevented while a message which requires a
response is active.
Documentation|libhexen: Todo comment wrt NetSv_SendLocalMobjState use in A_BishopAttack
Merge branch 'master' into common-episode-definition

Conflicts:
doomsday/plugins/common/src/g_game.cpp
Fixed|Doom|Intermission: Ultimate DOOM episode 2 animation discrepancies

Issue #1866