update ClamAV to 0.100.0

Update ClamAV to 0.100.0, which brings some new features and bugfixes
(release notes are available here: https://blog.clamav.net/2018/04/clamav-01000-has-been-released.html).

Since the internal LLVM code is now deprecated and disabled by default,
patching clamav/libclamav/c++/llvm/lib/ExecutionEngine/JIT/Intercept.cpp
does not seem to be necessary anymore.

Further, the --disable-zlib-vcheck option has been removed since it
produces warnings during compilation.

Signed-off-by: Peter Müller <peter.mueller@link38.eu>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>