Manuel and I were looking into a problem with applications failing to link

Manuel and I were looking into a problem with applications failing to link
(undefined reference to `main') when the .o file containing main was contained
in an static library(a '.a' ar archive).  It turns out that due to its single
pass nature, GNU ld was failing to pull it into the build.  This sticks a dummy
reference to main() into crt0.o, so that when an application is linked with the
main() function in a static library, we can be sure that main() actually gets
linked in.
 -Erik