Please add "dmstor" and other string<->coordinate functions to proj_api.h

[tvrusso]

This is a fairly trivial request, but back when projects.h was getting installed it was easy to write quick coordinate-manipulating programs for the command line using the dmstor function. Now that projects.h is not installed in 4.8.0, all of my old programs fail to build. It would be very nice if these simple string handling functions could be part of the public API, as they are pretty useful and it would be a pain to have to reinvent them.

I completely understand the need to have projects.h private, as manipulation of internal datastructures *should* be difficult, which is why I'm not asking for projects.h to be put back into the install. But as it is, the useful function dmstor (and its relatives such as rtodms) are now inaccessible. I'd also be fine with there being a public function with a more proj-specific prefix, as at least there'd be a work-around other than to install projects.h myself after building proj,writing my own version of dmstor/rtodms, or trying to get dmstor.c to build as part of my own projects (which itself is a problem given that it includes projects.h...).