#22 build fails with parallel make

[sam tygier]

building with
make -j2
or higher often fails with errors like:

rscal.o:rscal.f:(.text+0x2f6): more undefined references to `strget_' follow
collect2: ld returned 1 exit status
make[1]: *** [zgoubi] Error 1
make[1]: Leaving directory `/afs/hep.man.ac.uk/d/accelerators-ffag/sam/zgoubi/local-bzr/sam/trunk/zgoubi'
make: *** [all] Error 2

with the attached patch building is successful with highly parallel builds. (tested up to -j48 on a 48core server)

[sam tygier]