create integration test framework

This is a basic integration test framework for kpatch, which tests
building, loading, and unloading patches, as well as any other related
custom tests.

The kpatch-test script looks for test input files in the
tests/integration directory.  It expects certain file naming
conventions:

- foo.patch - patch that should build successfully

- bar-FAIL.patch - patch that should fail to build

- foo-LOADED.test - executable which tests whether the foo.patch module
  is loaded.  It will be used to test that loading/unloading the patch
  module works as expected.

Any other *.test files will be executed after all the patch modules have
been built from the *.patch files.  They can be used for more custom
tests above and beyond the simple loading and unloading tests.

I just have one test here, but many more to come eventually.  I'm
constantly doing manual testing of patches and am planning on automating
them with this framework.