Reading pre_process.inp fails with malformed file

[belericant]

Describe the bug
Some malformed case.py will be processed into a malformed pre_process.inp file that will fail to be successfully read into the namelist by read in s_read_input_file(). An undescriptive error message and a stack trace are shown upon program abort.

To Reproduce
One example of a malformed file:

1. Replace model_eqn in case.py with a non-numeric string
2. Run mfc.sh run path-to-case-py -t pre_process

Expected behavior
A clear error message informing the user of the malformed pre_process.inp file.

Proposed Fix
Check iostat flag and print an useful error message before aborting. E.g.:

if (iostatus /= 0) then
    backspace(1)
    read(1, fmt='(A)') line
    print '(A)', 'Invalid line in pre_process.inp around: '//trim(line)
    print '(A)', 'Exiting ...'
    call s_mpi_abort()
end if