Log Message:
Update to 2.3.1:

Just a simple maintenance release. User-visible changes include
one invalid #define fixed in the header file and the conditional
removal of the "Pointer" typedef to avoid name clashes and the
matching changes of the struct tmask.

Note: unless _XITYPEDEF_POINTER is defined, the Pointer typedef is
still there, so we're not breaking anything here. And the struct
tmask is only used by the server anyway and shouldn't be in the
header to begin with.