Ported fixes in previous commit from GTK2 to GTK3... Also dw_main_sleep() and dW_main_iteration() needed more complicated locking code on Linux... Due to Linux's use of fast mutexes double locking will deadlock, and calling dw_main_*() from a DW API function or callback before starting dw_main() might cause a double lock... We need to only lock the mutex if it isn't already locked by this thread.

# Set these here to change the version for all platforms
DW_MAJOR_VERSION=2
DW_MINOR_VERSION=2