Rework usermode PCI driver logic

- Meaningful messages about why drivers won't be built
  - State reasons drivers won't be built
  - If drivers can't be built but are explicitly requested, error out
  - If drivers can't be built but userland RT flavors requested, warn
- Check for hardy and write meaningful message
.gitattributes:  don't export git artifacts into tarball archives

This makes for a cleaner tarball for packages and releases
Submakefiles:  Add $(Q) to several linker commands
configure.in:  Look for tkConfig.sh in /usr/lib64 also

Red Hat location
linuxcncrsh tests:  use 'tcping' when no 'nc -z' available

Post EL6, netcat nc is replaced by nmap's ncat, which has no -z
equivalent arg.  tcping does the equivalent, so use it when available.

Note that the later use of nc is preserved.
configure.in:  replace 'tempfile' with distro-agnostic 'mktemp'