Ticket #4821: this change was suspected to be a fix, but it was not... however, the isLetter method is more clear now (TODO: making it more efficient)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@38191 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Put the local file reading back

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@38192 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e