Highlights:

• Avoid keywords (this, not) as variable names
• Move yyparse into config.h with other declarations
• All declarations in config.h are assumed guilty until proven innocent
• Some const-correctness
• Casting malloc/calloc returns

Note that we're not building any C++ here yet, this will be introduced
in other commits to replace some of the lib dependencies.

Sponsored by: Klara, Inc.
Sponsored by: NetApp, Inc.