JMZ says:

Add an emply MAIN__() function. This avoid an unresolved reference error
   during link phase when using fortran subroutines with non-fortran 'main()'.

Obtained from:  src/lib/libF77/MAIN.c rev 1.1 by jmz

gnu/lib/libg2c/MAIN.c

@@ -0,0 +1 @@
+MAIN__(){}