Fix build with CMake and GnuTLS and some work on Debian packaging.

Hi!

As far as I know if you try compile Zoneminder with GnuTLS you will get this error:

```
libzm.a(zm_rtsp_auth.cpp.o): In function `Authenticator::computeDigestResponse(std::string&, std::string&)':
zm_rtsp_auth.cpp:(.text+0x24e6): undefined reference to `MD5'
zm_rtsp_auth.cpp:(.text+0x2594): undefined reference to `MD5'
zm_rtsp_auth.cpp:(.text+0x26d8): undefined reference to `MD5'
libzm.a(zm_user.cpp.o): In function `zmLoadAuthUser(char const*, bool)':
zm_user.cpp:(.text+0x1115): undefined reference to `MD5'
collect2: error: ld returned 1 exit status
```

I made a little dirty fix for this but I don't know if there is a better way. I'm open to any suggestion.

On the other hand I worked to improve Debian package with some lintian love and changing to CMake.

Regards.