Teckyl: Print error with contents of lang::ErrorReport when parsing fails
Teckyl: Print error with contents of lang::ErrorReport when parsing fails

Currently, exceptions of the type `lang::ErrorReport` are handled as
unknown errors at the main function of the teckyl binary. This patch
catches such exceptions and prints the contents to `std::cerr` before
exiting with an error.

andidr/teckyl,andidr/teckyl,andidr/teckyl