Release 0.6.3 is a point release immediately following 0.6.2 because the master
branch would report flatcc --version as 0.6.2 instead of 0.6.2-pre prior to
the 0.6.2 release and version comment in generated headers would do the same.
By bumping to 0.6.3 ensures that 0.6.3 is indeeded a release version and not a
development snapshot. 0.6.3 is unctionally equivalent to the 0.6.2 release.