adding source files as CMake dependency to ROOT dictionary generation call

- changes in headers now result in a regeneration of ROOT dict
- addresses issue psi46/pxar#106
addresses build issue on WIN32 due to failing ROOT dict generation

-addresses issue psi46/pxar#105
-fixes regression introduced in 9d1a2e1b453a40847859f4b8b90882b23abf36fb