fail with math and multi

[Sarah Keating]

when an ASTNode contains a multi:xmlns, it gets removed by our API. The example is:

import libsbml
mathml = (
''
'<math xmlns="http://www.w3.org/1998/Math/MathML" '
'xmlns:multi="http://www.sbml.org/sbml/level3/version1/multi/version1">'
' a '
''
)
assert 'xmlns:multi' in mathml
ast_node = libsbml.readMathMLFromString(mathml)
new_mathml = libsbml.writeMathMLToString(ast_node)
print(new_mathml)
assert 'xmlns:multi' in new_mathml # FAIL