This commit adds -fdump-analysis which creates
a `$NAME-analysis.json` file with all of the finished
semantic analysis that the stage1 compiler produced.
It contains types, packages, declarations, and files.

This is an initial implementation; some data will be
missing. However it's easy to improve the implementation,
which is in `src/dump_analysis.cpp`.

The next step for #21 will be to create Zig code which parses
this json file and creates user-facing HTML documentation.

This feature has other uses, however; for example, it could
be used for IDE integration features until the self-hosted
compiler is available.