This fixes a design mistake made way back in 2009 (80e384598265) that for reasons now unknown used std::shared_ptr<T> to manage sysex and patch change canvas items.
In libcairo, colors are defined as 4 separate components, and each one is double between 0 and 1.
The arguments for `setvar` and `call` commands can be colors (like `#rrggbb`).
According to the OpenType specification of the 'cmap' table, the pair (0,6) for platform and encoding IDs is used for format 13 charmap tables.