Adds explicit arguments to the generator scripts to point to the input
such that they can be used in a hermetic build where the scripts do
not run from the source directory. Remaining inputs are assume to be
in the same directory.

Additional style changes include:

- checking the path for opening files rather than relying on exceptions.
- explicity define the type for and check for assignments to curropts
  array to enable static type checking of the code.
- adding missing includes in generated code.

Hermetic builds look for all necessary includes for the features used
in the header files. This commit adds the missing includes.

Python bindings required updating the arguments to the syntax_gen script.

Prints the OSError message.