Re-examined the problems of configuring a "minimal" library.
Synchronized the header files with the library code in order to assure that all the various conditionals (LIBXML_xxxx_ENABLED) were the same in both. Modified the API database content to more accurately reflect the conditionals. Enhanced the generation of that database. Although there was no substantial change to any of the library code's logic, a large number of files were modified to achieve the above, and the configuration script was enhanced to do some automatic enabling of features (e.g. --with-xinclude forces --with-xpath). Additionally, all the format errors discovered by apibuild.py were corrected. * configure.in: enhanced cross-checking of options * doc/apibuild.py, doc/elfgcchack.xsl, doc/libxml2-refs.xml, doc/libxml2-api.xml, gentest.py: changed the usage of the <cond> element in module descriptions * elfgcchack.h, testapi.c: regenerated with proper conditionals * HTMLparser.c, SAX.c, globals.c, tree.c, xmlschemas.c, xpath.c, testSAX.c: cleaned up conditionals * include/libxml/[SAX.h, SAX2.h, debugXML.h, encoding.h, entities.h, hash.h, parser.h, parserInternals.h, schemasInternals.h, tree.h, valid.h, xlink.h, xmlIO.h, xmlautomata.h, xmlreader.h, xpath.h]: synchronized the conditionals with the corresponding module code * doc/examples/tree2.c, doc/examples/xpath1.c, doc/examples/xpath2.c: added additional conditions required for compilation * doc/*.html, doc/html/*.html: rebuilt the docs