Print the name pattern in the error message when a declaration has to be ignored because of an error

[sonmarcho]

It happens that we can't extract a declaration at all and have to ignore it. For instance, if we encounter an error when translating the signature of a function, we ignore it and print the following message:

[ERROR] ... ERROR ...
[ERROR] Could not translate the function 'foo' because of previous error

It would be useful to add the name pattern (the Rust name identifying a definition) in the error message. This would be especially useful to add builtin support for external declarations which fail to extract.

[Nadrieril]

Fixed by #199 but it would be nice to add a negative test for that when we get them