So far `std.jsonnet` needed to be updated seprately from
the cpp-jsonnet submodule. Since we should update it anyway
at the same time (to make sure the tests are running fine),
we can just as well get it directly from there, eliminating
the extra step of copying the new `std.jsonnet` version.
This change updates the cpp-jsonnet used.
Current go-jsonnet is not really 0.12.1 - it even
reports 0.12.0. This brings all the good stuff
from recent cpp-jsonnet commits and actually syncs
the version.
Change the dump code so that it hides the values of variable
definitions if they're large. This means that godoc.org should
be able to deal with the output, and the godoc output is
readable without needing to read through a huge struct literal definition.
Other approaches might be to always generate an extra variable
(seems unnecessary) or to pass to writer explicitly to the dump
methods rather than swapping s.w out temporarily. The former
seems unnecessarily intrusive to the usual output; the latter
seemed unnecessarily intrusive to the source itself.
YMMV.
