e-xml: Add include guards to header files
e-xml: Add C api
e-xml: Add example program that uses C bindings
Add ChangeLog entry
Merge branch 'pr-xml-c-api-2' of https://github.com/olajep/epiphany-libs into olajep-pr-xml-c-api-2

Conflicts:
	ChangeLog
	src/e-xml/Makefile
Merge branch 'olajep-pr-xml-c-api-2'