Use SSDATA when the context wants char *.

Use SSDATA when the context wants char *.

* alloc.c, buffer.c, bytecode.c, callproc.c, dired.c:
* dispnew.c, doc.c, editfns.c, emacs.c, fileio.c, filelock.c:
* fns.c, font.c, frame.c, image.c, indent.c, keyboard.c:
* lread.c, minibuf.c, print.c, process.c, search.c, widget.c:
* xdisp.c, xfaces.c, xfns.c, xml.c, xselect.c, xterm.c:
Use SSDATA (not SDATA) when the context of the expression wants
char * (not unsigned char *).