[Hallcsw] changes to SIMC code shms/mc_shms_hut.f

[Mark Jones]

Unfortunately I found that I had left in some code
in shms/mc_shms_hut.f which I had been using to do
some special test. When setting flags to use the helium bag
in the SHMS hut I had hardwired "ms_flag = .true." before
helium bag section of code and the ms_flag = .false. afterwards
so that I could study the multiple scattering in helium
bag by itself. I have removed these statements.
Sorry about this.

Also I modified in shms/hut.inc
	parameter (hscin_1y_top   = -45.)
	parameter (hscin_1y_bot   =  45.)
	parameter (hscin_2y_top   = -57.5)
	parameter (hscin_2y_bot   =  57.5)
	parameter (hcer_top      = -55.00)
	parameter (hcer_bottom   =  55.00)

to make them vertically symmetric about the central ray of the SHMS.
The drift chambers were already modified to be symmetric.
Previously , we had the detector's offset by 5cm in the vertical,
but with the modified dipole offset that it is better to
have them centered. One gains acceptance at negative delta.

So for simc_gfortran you can updated
shms/hut.inc and shms/mc_shms_hut.f

For the SHMS single arm MC, I posted a new tar file at
  https://hallcweb.jlab.org/wiki/index.php/SHMS_Single_arm_Monte_Carlo


                 Cheers,
                          Mark