PGF and NAG behaviour in ropp_io_thin.f90

[Huw Lewis]

Bugs found with PGF and NAG compilers in ropp_io_thin.f90.

• these compilers require an explicit format statement in conversion from string to real for determining number of thinned levels and thinned heights (see 'FIXME' comments in code). Note previously found problems in using CASE with these compilers in this routine.

The original code works fine with all other compilers, and the bug cannot be replicated in simple test programs run with nag.

Need to investigate what in particular is distinct about the ROPP code (cf test routines) which causes this performance, and find more satisfactory long-term solutions, i.e. input thinning information need not be of particular format.