Build Bug: -lm should come after passing ../common/libor.a to linker

The following commit:

    commit e56747f9
    Author: Nick Mathewson <nickm@torproject.org>
    Date:   Tue Dec 15 14:32:55 2009 -0500

        Refactor a bit so that it is safe to include math.h, and mostly not needed.

introduced this line:

    tor_resolve_LDADD = -lm ../common/libor.a @TOR_LIB_WS32@

which caused the build to fail, because only ../common/libor.a
(via the embedded ../common/util.o via ../common/util.c)
referenced libm's `lround' and `log' symbols, so that the
linker (GNU ld) didn't bother to import those symbols before
reading ../common/libor.a, thus leaving those symbols undefined.

The solution was to swap the order, producing the line:

    tor_resolve_LDADD = ../common/libor.a -lm @TOR_LIB_WS32@

Signed-off-by: Michael Witten <mfwitten@gmail.com>