Prompted by CVE-2021-3541, but this includes an awful lot of serious bug
fixes by Nick and others.
- configure.ac: bumped to new release
- doc/* updated and regenerated
* doc/Makefile.am: make the check for symbols pbm a make api failure
* doc/symbols.xml: added xmlXIncludeProcessTreeFlagsData
* doc//* elfgcchack.h libxml2.syms testapi.c: regenerated
* valid.c: fixed a weird error where validity context whould not
show up if warnings were disabled pointed out by Bob Stayton
* xmlIO.c doc/generator.py: cleanup and fix to regenerate the docs
* doc//* testapi.c: rebuilt the docs
Daniel
* libxml.spec.in doc/devhelp/*: finished the integration with
devhelp, completing the index and inserted into the gtk-doc
database at "make install" stage
Daniel
