Data files can be added in the data/ subdirectory, with the following
naming conventions:

 * files belonging to the same test share the first 6 characters of their name
 * the 7th character is an underscore
 * original file name ends with 1.xml
 * modified file name ends with 2.xml
 * result file names end with _result, and can contain command line
options to be passed to xmldiff separated with underscores

Example:

test02_1.xml
test02_2.xml
test02_result
test02_--xupdate_result

-- Alexandre Fayolle
