Notice newer cppcheck versions are slower. In order to make the check fit
on travis-ci I had to make a few extra changes:
- better optimization flags when building cppcheck
- force a number of ifdefs in the check

Now master takes approx 25 minutes, so we have room for adding new code.

cc: @gtribello

Fixed a typo in keyword

./configure --disable-shared was giving an error upon install
due to a missing file

just annoying when there are directories whose name contains a space
within the src/ directory

see #227

Notice that without the fix this test fails.

backport of 4a96057e

thanks to @valsson

(still a stylistic warning)

Check first if astyle is present. In this way, when astyle is not compiled,
we get a single error instead of one error per file.