[SG2] Combining support weapons in a single fire action

SG2 as written doesn't allow you to do this.  However, poking through
the US M249 SAW Field Manual, I see them describing engaging targets
with a pair of riflemen.  See:

http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/23-14/fm231_7.htm#REF67h3