feat(codegen): More readable names for common a-b variables
feat(codegen): More readable names for common a-b variables

Names of the form `a-b-c` got compiled to `_a$45_b$45_c`. These
names are more widely used in Siren code, so it makes sense to
make them a bit more easier to read (although the whole output
is pretty much unreadable right now).

siren-lang/siren,mermaid-language/mermaid