trafgen: Replace variable length arrays

Use zmalloc()'ed buffer or statically sized array to replace usage of
variable sized arrays. Found by the sparse static checker.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
build: Add continuous integration support via travis-ci

This allows any libnl github repo to link to travis-ci which
will result in new commits and pull requests to be automatically
built with both gcc and clang. Any build failures including the
addition of warnings are reported to the author and committer.

Following Thomas Graf's suggestion:
https://plus.google.com/103961622207897185587/posts/GaVC6jwcMgp

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
mausezahn: Fix non-ANSI function declarations

ANSI C doesn't allow empty parameter list, thus use void where
appropriate. This fixes the corresponding sparse warning.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
build: travis: Install dependencies before build

In order to make sure all tools (except curvetun) are built by Travis
CI, install the libraries they depend upon.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
build: travis: Pass on CC environment variable to make

If travis compiles with clang, the environment variable CC is set. Since
the netsniff-ng build system doesn't currently pick it up unless
explicitly specified as a make variable, pass it on as such.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
build: travis: Disable clang for now

clang doesn't understand all our (GCC-spcific) compiler flags. We need
to work around it by filtering them out properly in case clang is used.
For now, just disable clang on travis, until I figured this out locally.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Merge remote-tracking branch 'upstream/master'