Import patch from PR 262877 to enable symbol versioning

Import following upstream commits:
5c71ada83acf30dc7e8ca8fca1f025c7dd014447 (partially)
141d784ecffaf00f152f8a7c627e72f72d398f34 (replaces local patch)
6d10df7c5c6a098078db8a7649d5d9a1f820d9cd (replaces local patch)
f2987a295ff847ecb2a6a3eae1a271c9a64255b6
94ac5e61f399759a5463c0505099222ed8f13a82 (fixes PR 263094)

Add alternative variant of upstream commit
28d0399682027cc65dd17ac675bde85a11e5a01e (remove xsa file)

CFLAGS and INCLUDEDIR no longer refers to ${PREFIX}/include 
in bin/xml2-config , libxml-2.0.pc or lib/xml2Conf.sh (fixes PR 262824)