ADDED: Flymake integration in sweeprolog-mode

ADDED: Flymake integration in sweeprolog-mode

* sweeprolog.el:
- sweeprolog-enable-flymake: new user option.
- sweeprolog--diagnostics: new buffer-local variable.
- sweeprolog--diagnostics-report-fn,
sweeprolog--diagnostics-changes-beg,
sweeprolog--diagnostics-changes-end: new buffer-local variables.
- sweeprolog-defface: add docstrings for generated functions.
- sweeprolog--colourise: accumulate diagnostics when
sweeprolog-enable-flymake is non-nil.
- sweeprolog-colourise-buffer, sweeprolog-colourise-some-terms: report
diagnostics when sweeprolog-enable-flymake is non-nil.
- sweeprolog-show-diagnostics: new command in sweeprolog-mode buffers.
- sweeprolog-mode-map: bind it.
- sweeprolog-diagnostic-function: new function.
- sweeprolog-mode: use it when sweeprolog-enable-flymake is non-nil.
* README.org: Examining diagnostics: new section.
* NEWS.org: announce flymake integration.