make check: Change from sparse to cppcheck as default backend.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
parse-conf.c:pop_token() - Fix possible NULL pointer dereference

Thank you cppcheck.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
ifvc.c:iface_find_by_vif() - Reduce scoping of local variable.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
mcgroup.c: Remove unused local varibles.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
mcsender.c: Add field width specifier to sscanf() to limit user input.

cppcheck report:

         [mcsender.c:74]: (portability) scanf without field width limits
         can crash with huge input data on libc versions older than
         2.13-25. Add a field width specifier to fix this problem: %i =>
         %3i

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
smcroute.c: Reduce scoping of local variables.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
Fix hidden problem with dynamic interfaces, thanks to cppcheck.

The clever cppcheck tool alerted to this:

    [smcroute.c:178]: (style) Variable 'iface' is assigned a value that
    is never used.

Turns out there was unfinished code that was supposed to check if
inbound traffic for (*,G) handling was from an unknown interface.

Add check for unknown interface, possibly dynamically added after
smcroute was started.  We don't support such interfaces right now,
but it could easily be added.

For some people it could be useful to instead exit on this error,
and let a process supervisor restart smcroute so it reenumerates
and picks up that dynamic interface.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
smclog(): Fix nasty uninitialized variable used in vsnprintf() buf calculation.

Again, cppcheck found this:

    [syslog.c:54]: (error) Uninitialized variable: len

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>