Add "compile everything" tool

Having many tests is quite futile if they aren't executed once in a
while<sup>[citation needed]</sup>.

Alas, this is not the purpose of this PR. This PR adds the tool
"compile_test.py", which executes `make buildtest` for all applications
in `examples` and `tests`, and prints a comprehensive list of the
results.
Merge pull request #1048 from Kijewski/compile_test

Add "compile everything" tool