Exclude *.c files from make doc
Exterminate old-style function definitions
Exterminate old-style function declaration/prototypes
make: add own file for CFLAGS feature tests
make: fast out on old-style function definitions
sys:crypto: put ciphers into one module
unittests: separate test suites from main.c

This change removes the need to patch the main.c if you add or remove a
test suite. A test suite in `tests/unittests/tests-XXX` needs to export
the function `void tests_XXX(void)`, which gets called by `main()`.

The `tests-XXX/Makefile` looks like your average module:
```
MODULE = tests-XXX
include $(RIOTBASE)/Makefile.base
```
Merge pull request #1124 from Kijewski/consolidate-crypto

sys:crypto: put ciphers into one module
Merge pull request #1119 from Kijewski/error_old-style-definition

Exterminate old-style function definitions
sys/crypo: fix function declarations

In #1119 old-style function declarations are exterminated and forbidden.
I missed the functions in `sys/crypto` because they weren't used
throughout the tests/examples before #1124.
Merge pull request #1170 from Kijewski/fixup-1119-1124

sys/crypo: fix function declarations
examples: added README.md to ipc_pingpong example
added iot-lab_M3 and temporarily dropped telosb support; split patch.txt
into separate patch files
examples: adjusted output and README for IPC pingpong
Merge pull request #1056 from thomaseichinger/pkg-openwsn

pkg: openwsn: update with iot-lab_M3 support and split patch files
examples: IPC ping-pong README adjustments
Merge pull request #1171 from haukepetersen/example_ipcpingpong_readme

examples: added README.md to ipc_pingpong example
native: fixup #1145: function declaration
Merge pull request #1172 from Kijewski/fixup-166b88f1

native: fixup #1145: function declaration
Merge pull request #1168 from Kijewski/unittests-use-subfolders-and-dark-magic

unittests: separate test suites from main.c