* doc/apibuild.py doc/elfgcchack.xsl: revamped the elfgcchack.h
format to cope with gcc4 change of aliasing allowed scopes, had
to add extra informations to doc/libxml2-api.xml to separate
the header from the c module source.
* *.c: updated all c library files to add a #define bottom_xxx
and reimport elfgcchack.h thereafter, and a bit of cleanups.
* doc//* testapi.c: regenerated when rebuilding the API
Daniel