Updated to build against xorg-x11-server 1.16.0.

For #25.

I wasn't able to make cmake happy when testing this so you might want to check it compiles OK.
Also needs `#if`:

```
vncHooks.cc: In constructor 'GCFuncUnwrapper::GCFuncUnwrapper(_GC*)':
vncHooks.cc:828:30: error: invalid conversion from 'const GCFuncs*' to 'GCFuncs*'
vncHooks.cc:830:30: error: invalid conversion from 'const GCOps*' to 'GCOps*'
vncHooks.cc: In constructor 'GCOpUnwrapper::GCOpUnwrapper(_Drawable*, _GC*)':
vncHooks.cc:909:30: error: invalid conversion from 'const GCFuncs*' to 'GCFuncs*'
vncHooks.cc:910:28: error: invalid conversion from 'const GCOps*' to 'GCOps*'
vncHooks.cc: In destructor 'GCOpUnwrapper::~GCOpUnwrapper()':
vncHooks.cc:914:18: error: invalid conversion from 'const GCFuncs*' to 'GCFuncs*'
```