add an --with-coverage configure option and a 'make cov' target based on * configure.in Makefile.am: add an --with-coverage configure option and a 'make cov' target based on gcc profiling and the lcov tool. Currently at 68.9% coverage out of 'make check' and runsuite executions. * xmlreader.c: remove warnings due to C++ comments Daniel svn path=/trunk/; revision=3780