main: Add openconnect_vpninfo_free() on a couple of exit paths

This makes it easier to check for library memory leaks.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
buildsys: Allow overriding -W flags

For any given source file, automake will apply either
"$(AM_CFLAGS) $(CFLAGS)" or "$(objname_CFLAGS) $(CFLAGS)" [1].  Move the
warning flags into the former item so that they can be disabled on a per-
object basis.

[1] http://www.gnu.org/software/automake/manual/automake.html#Flag-Variables-Ordering

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
acinclude: Add AX_JNI_INCLUDE_DIR macro

AX_JNI_INCLUDE_DIR is used to locate jni.h for building the Java Native
Interface to libopenconnect.  Original source:

http://www.gnu.org/software/autoconf-archive/ax_jni_include_dir.html

This commit also includes two pending enhancements:

http://savannah.gnu.org/patch/?8154
http://savannah.gnu.org/patch/?8155

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
JNI: Initial commit of C wrapper functions

If the user runs "configure --enable-java", a separate library is built
with Java native interface stubs and it can be loaded with:

    System.loadLibrary("openconnect-wrapper");

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
JNI: Initial commit of Java library + example program

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>