Require libXi 1.2 and inputproto 1.5.

Require libXi 1.2 and inputproto 1.5.

Device properties are available in a released libXi version now, so there's no
need to keep them conditional, make 1.5 mandatory.

We also have the explicit check for XI2 functions in libXi, so there's no need
to have requirements for inputproto 1.9.99.5.