There is a separate file thread_wince.h for use with CE, but that is
firstly not used due to a missing macro definition and secondly it
doesn't compile as it is. The attached patch defines WINCE_THREADS for
CE and makes the file at least compile.

Note that this doesn't touch any working code, because the CE port is
currently broken anyway. Further, the changes compile, but since there
are various other bits and pieces still missing, it is impossible to
test it yet.