S = READ_NAMELIST (FILENAME) returns the struct S containing namelists and
 variables in the file FILENAME organised in hierachical way:

                |--VAR1
                |--VAR2
   |-- NMLST_A--|...
   |            |--VARNa
   |
   |            |--VAR1
   |-- NMLST_B--|--VAR2
   |            |...
 S --|     ...    |--VARNb
     |
     |            |--VAR1
     |-- NMLST_M--|--VAR2
                  |...
                  |--VARNm

 Note:  The function can read multidimensional variables as well. The  
 function assumes that there is no more than one namelist section per 
 line. At this time there is no syntax checking functionality so the 
 function will crash in case of errors.

 Example:
     NMLST = read_namelist ("OPTIONS.nam");
     NMLST.NAM_FRAC.XUNIF_NATURE = 0.1;
     write_namelist(NMlST, "MOD_OPTIONS.nam");

Package: io