Fix various problems with the timer code. * SDL_timer_running wasn't always updated correctly. * Fixed occasional crash in SDL_SetTimer() when clearing threaded timers * It was possible to get both the timer thread and event thread running * Other misc. cleanup

## Makefile.am for the dummy cdrom driver for SDL

noinst_LTLIBRARIES = libcdrom_dummy.la
libcdrom_dummy_la_SOURCES = $(SRCS)

# The SDL cdrom driver sources
SRCS =  SDL_syscdrom.c