Add --enable switch for documentation build, build documentation by
default and add a few more configure tests.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Check for and prefer libev over libevent and check for the location
of the event.h file, which is contained in libev/event.h on Fedora.
Signed-off-by: Patrick McHardy <kaber@trash.net>