A group containing 'all' was not checked for minOccurs<=1, so later a fatal...

A group containing 'all' was not checked for minOccurs<=1, so later a fatal error 'unknown content spec type' would be reported instead of the correct 'group with all must have minOccurs==1'

git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@709133 13f79535-47bb-0310-9956-ffa450edef68