Add multiple build support styles

Add multiple build support styles

* Add RPM and DEB packaging targets (using CPack from CMake) to build
  binary packages for Fedora and Ubuntu targets.
* Add Docker build scripts for each of the above that run the build in
  the right environment (assuming docker is available).
 - In Ubuntu, build against the LLVM 3.7 nightly snapshots
 - In Fedora, build against LLVM 3.7 from git (takes longer)
* Depending on packages installed on the build machine, it may be
  possible to cross-package for other targets without invoking Docker.
* Re-introduce src/cc/compat directory to keep the build stable for the
  time being. Similarly, it was necessary to #define some ugly constants
  that should eventually show up in libc.
* Add a few simple version checks to allow a partially working (really
  tracing only) libbcc in 4.1 kernels.

TODO (followup commit): Re-work the READMEs

Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>