Fix for compilation errors for BcVegPy and GenXicc with gcc8 (LHCBGAUSS-1688)

This MR fixes compilation of BcVegPy and GenXicc with gcc8 in the lhcb-head nightly slot. I had to fiddle with dimensions of some 2D arrays which are passed to function where it is used as 1D array. Given that and the fact that I'm not as fluent in FORTRAN as I used to be we should do validation with appropriate event types to verify that I did not make mistake.