Hardcoded out of date version number suffix in library filenames

Inspect configure and configure.in, then reproduce the issue with ./configure && make all install and alr get xmlada. Trace where the 18.0w suffix is selected; done means manually built library filenames use the intended version rather than an outdated hardcoded value, with an overridable version if supported by the project.

When xmlada is built with the usual method of ./configure && make all install, all produced xmlada library files are suffixed with 18.0w - due to that version being hardcoded into configure script (& configure.in)

lrwxrwxrwx   1 cpigott domain users   53 Oct  7 15:42 libxmlada_dom.so -> ../lib/xmlada/xmlada_dom.relocatable/libxmlada_dom.so
lrwxrwxrwx   1 cpigott domain users   59 Oct  7 15:42 libxmlada_dom.so.18.0w -> ../lib/xmlada/xmlada_dom.relocatable/libxmlada_dom.so.18.0w
lrwxrwxrwx   1 cpigott domain users   65 Oct  7 15:42 libxmlada_input_sources.so -> ../lib/xmlada/xmlada_input.relocatable/libxmlada_input_sources.so
lrwxrwxrwx   1 cpigott domain users   71 Oct  7 15:42 libxmlada_input_sources.so.18.0w -> ../lib/xmlada/xmlada_input.relocatable/libxmlada_input_sources.so.18.0w
lrwxrwxrwx   1 cpigott domain users   53 Oct  7 15:42 libxmlada_sax.so -> ../lib/xmlada/xmlada_sax.relocatable/libxmlada_sax.so
lrwxrwxrwx   1 cpigott domain users   59 Oct  7 15:42 libxmlada_sax.so.18.0w -> ../lib/xmlada/xmlada_sax.relocatable/libxmlada_sax.so.18.0w
lrwxrwxrwx   1 cpigott domain users   59 Oct  7 15:42 libxmlada_schema.so -> ../lib/xmlada/xmlada_schema.relocatable/libxmlada_schema.so
lrwxrwxrwx   1 cpigott domain users   65 Oct  7 15:42 libxmlada_schema.so.18.0w -> ../lib/xmlada/xmlada_schema.relocatable/libxmlada_schema.so.18.0w
lrwxrwxrwx   1 cpigott domain users   61 Oct  7 15:42 libxmlada_unicode.so -> ../lib/xmlada/xmlada_unicode.relocatable/libxmlada_unicode.so
lrwxrwxrwx   1 cpigott domain users   67 Oct  7 15:42 libxmlada_unicode.so.18.0w -> ../lib/xmlada/xmlada_unicode.relocatable/libxmlada_unicode.so.18.0w

This is an issue when building xmlada manually, i.e. getting the release archive via alr alr get xmlada (my particular usecase is using it as a dependency of libadalang)

At the very least the version should be overridable, which it isn't as far as I can see (I might be missing something)

(This doesn't appear to be an issue with GNAT Pro distributions of xmlada, so they are presumably being built via other methods)