This adds debugging symbol generation for boxes, bare functions, vectors, and strings, along with a tests for boxes and vectors.
Note that gdb will see them as their actual compiled representation with the refcount, tydesc, etc. fields, so if `b` refers to box, `b->boxed` will refer to its value. Also, since you seem to use the [C struct hack](http://c-faq.com/struct/structhack.html) for dynamic vectors, you won't be able to print out the whole vector at once, only one element at a time by indexing specific elements.
This is due to the way different versions of gdb print out structs: older versions have them always spread out with fields on different lines, while newer versions will compactly print them on one line. This makes it hard for the output checker to verify the expected output.
