Our gimp-win-x86 job fails with the following error:
../modules/gimpinputdevicestore-dx.c:207:28: error: passing argument 2
 of 'GetModuleHandleExW' from incompatible pointer type
 [-Wincompatible-pointer-types]

Fairly Recent the call to `GetModuleHandleEx` was changed to
`GetModuleHandleExW`. This new call expects a wide char pointer
instead of a char pointer.
So replace it with the wide variant (LPCWSTR). Since in this call
an address is actually expected, the actual contents don't need to
be a wide string.