CFITSIO Group module README

1. All functions have names of the form 'ffgt##' or 'ffgm##', where "gt" is
for Group Table and "gm" is for Group Member.

2. The only nonstandard CFITSIO function that is called from group.c is the
fits_parse_input_url(), and this is called from a single non-API function
void ffgtcn(char *filename)

3. Two of the functions, ffgtcp() (copy a grouping table) and ffgtrm() (remove
a grouping table), have the option to operate recursively. This makes them
_potentially_ dangerous to use as the recursion could run-away if applied to
poor situations. The major danger is that a grouping table has itself as a 
member when the copy or remove is performed; however, both routines guard
against this by keeping track of all HDUs copied or deleted via the HDUtracker
struct.

4. All the functions try to insert null values into columns when information
for a given member is not defined. For the integer cols the null value is a
0. For ascii cols the null value is a null string "\0". The only way that I
could get a NULL character to be placed in the ascii columns is to call
fits_write_col_byt() and force the placement of the NULL character. Is there
some better way to do this?

5. Nine group module specific error codes are defined in group.h. Please 
re-number them to fit into the cfitsio scheme as you see fit.

6. The grouptest.c function gives the group module a good workout and results
in three fits files being created (test1.fits, test2.fits, test2.fits).


