[fortran,patch] Don't write common more than once in a module file (PR 30285)

[Bud Davis]

is there anyplace we could store the fact that a common has been written ?  

maybe store the pointer to the filename into the common record, then you could compare the
pointers and if they match, not write....

went down this same path many months ago, and felt that saving off a list of what was written was
a bag on the side of a kludge :):)

of course, a patch that works beats an elegant idea every time.....


just my 2 cents...


--bud davis