In ={hello} world= and ~hi {0} {1} {2}~, "{hello}" and "{0}" etc. are expected
to be exported verbatim. However, currently they are exported to "{{{hello}
world}}" and "{{hi {0} {1} {2}}}" respectively. As a result, "{hello}", "{0}"
etc. are treated by confluence wiki as macros and hence cause errors like
"Unknown macro: {hello}".
This fix is to escape the openning curly braces, i.e. adding a back slash before
them. The results are "{{\{hello} world}}" and "{{hi \{0} \{1} \{2}}}".