[PATCH] Fix libgfortran on darwin, hpux and cygwin (PR libfortran/24991)

[Jack Howarth]

    Is anyone on any other archs seeing timeouts in the fgetc_1? On Darwin
8.3.0 with Jakub's proposed patch as well as when I regress the changes from
http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=106704 instead, I see
the fgetc_1 and associated tests hang. A run of fgetc_1 in gdb shows that
the hang occurs on the third call to...

91            memmove (dest, src, destlen);

...which never returns any information back to the debugger. This
code appears to be called from __gfortran_copy_string in 
libgfortran/intrinsics/string_intrinsics.c.
                Jack