Move temporary bitmap descriptor onto bm_load_sub stack
Remove useless allocation when saving screenshot
Move close_autosave delname onto stack
Move autosave_mine savename onto stack
Move medkey_init LispCommand onto stack
Move ai_save_state *_rw onto stack
Move kmatrix_screen onto kmatrix_view stack
Fix technical buffer overrun in drive letter selection

Padding makes this safe, but moving onto the stack is cleaner.
Move drive letter newmenu_item onto select_file_handler stack
Move briefing tmp buffer onto load_mission stack
Move ending tmp buffer onto load_mission stack
Move callsign buf onto change_playernum_to stack
Move grs_bitmap BBM onto piggy_new_pigfile stack
Move object_rw onto state_save_all_sub stack
Move object_rw onto state_restore_all_sub stack
Move file search paths onto PHYSFSX_addArchiveContent stack
Move demo file mount paths onto PHYSFSX_addArchiveContent stack
Move file search paths onto PHYSFSX_removeArchiveContent stack
Move demo file mount paths onto PHYSFSX_removeArchiveContent stack
Move movie control structure onto RunMovie stack