build: fix packaging problems and make distcheck happy

The 'distcheck' rule performs all of the operations associated with
packaging a distribution and verifying that the distribution works.

There were several problems:

  - libgsmhr/Makefile.am: 'patches' dir was not listed in EXTRA_DIST
  - libgsmhr/Makefile.am: (dist)clean targets wan't defined properly
  - tests/Makefile.am: 'ref-files' dir was not listed in EXTRA_DIST
  - tests/testsuite.at: wrong path was used for io_sample.txt

Change-Id: Ieb8f6a2a81f9b75c8c6c5db443b0e7be02bc4153
3 files changed