Note that some of the graphviz functions have backwards incompatible changes
that might also affect other clients of the PGF run-time library.
Also added graphvizDefaults and export it together with GraphvizOptions from
the PGF run-time library.
+ Make room for function names in the BracketedString data structure.
+ Fill in function names when linearizing an abstract syntax tree to a
BracketedString.
+ Fill in wildCId when it is not obvious what the function is.
+ Function bracketedLinearize: for compatibility with the other linearization
functions, return Leaf "" instead of error "cannot linearize".
+ Export flattenBracketedString from module PGF.
+ PGFServce: make function names available in the JSON representation of
BracketedString.
