run flexpart use fnl data

寒江雪（王训

If I am not wrong, thesolution for FNL setting should be nxshift=0 in par_mod.f90 and change "xaux2=xaux2in" to "xaux2=xaux2in+360" in gridcheck_gfs.f90. Because the xaux1in and xaux2in of FNLdata  are 0 and -1, written out from gridcheck_gfs.f90, which aredifferent from the GFS values of 0 and 359. So for FNL data, if wiouththis modification, gridcheck_gfs.f90 failed to transform data from 0--359 to-179--180, leading to failure in check in the readoutgrid.f90 (xlon0 stillequal to 0 not -179). Anyway, I think we should use nxshif=0, if we use_gfs.f90 subprogram for compiling.