0.17 build broken with GCC 8.3

One of you recent backports to GCC 8.3 broke the 0.17 build. The GCC version check needs to be adjusted.

--- gcc-python-plugin-0.17.orig/gcc-python-pretty-printer.c +++ gcc-python-plugin-0.17/gcc-python-pretty-printer.c @@ -46,8 +46,8 @@ PyGccPrettyPrinter_New(void) Use placement new to run it on obj->pp. / new ((void)&obj->pp) pretty_printer( -# if (GCC_VERSION < 9000)

/ GCC 9 eliminated the "prefix" param. / +# if (GCC_VERSION < 8003)
/ GCC 8.3 eliminated the "prefix" param. / NULL,
endif
```
                0);
```

davidmalcolm / gcc-python-plugin

0.17 build broken with GCC 8.3 #173

endif