Merge branch 'pr#34'

src/@x13/clean.m

src/@x13/print.m

src/@x13/subsasgn.m

src/@x13/subsref.m

src/@x13/x13.m

src/utilities/x13/checkcommandcompatibility.m

src/utilities/x13/checkoptioncompatibility.m

src/utilities/x13/isoption.m

src/utilities/x13/printoption.m

src/utilities/x13/printspan.m

src/utilities/x13/printstart.m

src/utilities/x13/setdefaultmember.m