Fixes#35.
Add a helper to escape C++ string literals so that JSON control characters
(\n, \r, \t, and other bytes below 0x20) are emitted as escape sequences
instead of raw bytes. Use it for:
- field comments that include the JSON property key
- object key comparison literals in matchKey()
- enum name arrays
Also add regression tests that generate and syntax-check headers for
schemas containing newlines and other control characters in property keys
and enum values.
weaselbot