Completion of error handling

[elfring]

Would you like to add more error handling for return values from functions like the following?

• fclose ⇒ output
• fprintf ⇒ write_signames
• fputs ⇒ main

[mgree]

These are all just part of dash, so this isn't the right place for a PR on them---you want https://git.kernel.org/pub/scm/utils/dash/dash.git/, the upstream repo for dash.

http://vger.kernel.org/vger-lists.html#dash is the mailing list if you want to check in about that.