buildtest: ignore empty folders

`compile_test.py` fails if there are empty folders in `/examples` or
`tests`. This is not a problem for Travis, because it always has a clean
repo.

For the average users there is a problem if they work on multiple
branches and one branch has new examples or tests. If they don't delete
the residual `bin` folders, then `compile_test.py` will print out these
applications as having failed.

This change checks for the existence of a `Makefile` in the application
folder. Also I added a progress indicator, because I like it. :)
core: prefix API functions correctly

Also changed names for bitarithm functions and rename thread_pid to sched_active_pid.
Merge pull request #1000 from OlegHahm/prefix_core_api_functions

core: prefix API functions correctly
documentation: fix CMSIS doxygen for SAM3x8e
documentation: fix doxygen group for Z1
Merge pull request #1202 from OlegHahm/cortex_doxygen_cleanup

documentation: cleanup doxygen for SAM3x8e and Z1
Fix application name for test_bloom_byte application
Merge pull request #1212 from authmillenon/fix-application-names

Fix application name for test_bloom_byte application
msp430: workaround: define errno values if not provided by MSP430 lib
Merge pull request #1189 from Kijewski/compile_test-empty-folders

buildtest: ignore empty folders
Merge pull request #1213 from OlegHahm/ubuntu_msp430_errno_fix

msp430: workaround: define errno values if not provided by MSP430 lib
msp430: provide oneway-malloc implicitly

For MSP430 boards oneway-malloc is already used *if* `malloc.h` was
included. The problem is that `malloc.h` is not a standard header, even
though it is common. `stdlib.h` in the right place to look for
`malloc()` and friends.

This change removes this discrepancy. `malloc()` is just named like
that, without the leading underscore. The symbols now are weak, which
means that they won't override library functions if MSP's standard
library will provide these functions at some point. (Unlikely, since
using `malloc()` on tiny systems is less then optimal ...)

Closes #1061 and #863.
Add doxygen comments to MSP's oneway malloc
msp/tests: remove blacklist from test_bloom_bytes

Issue #1061 was fixed.