find . \( -name \*.xul \
    -o -name \*.inc \
    -o -name \*.mn \
    -o -name \*.rdf \
    -o -name \*.xml \
    -o -name \*.in \
    -o -name \*.cpp \
    -o -name \*.h \
    -o -name \*.idl \
    -o -name \*.dtd \
    -o -name \*.properties \) -exec dos2unix -U {} \;

Just try to run the XUL preproc on a #include for a file having DOS end of lines and you'll know what I mean...