Rename Input.h to vncInput.h to fix building on case-insensitive FS

Rename Input.h to vncInput.h to fix building on case-insensitive FS

I am cross-compiling from macOS for a FreeBSD-derived system so my host
file system is case insensitive but the target isn't. Without this change
I get the following warnings which show that the vnc "Input.h" is being
included from mi/mi.h instead of the xserver "input.h":
```
In file included from /Users/alex/cheri/xvnc-server/hw/vnc/Input.c:33:
/Users/alex/cheri/xvnc-server/mi/mi.h:55:10: warning: non-portable path to file '"Input.h"'; specified path differs in case from file name on disk [-Wnonportable-include-path]
#include "input.h"
         ^~~~~~~~~
         "Input.h"
```