This brings together the two libraries back into one now that the whole
design is pretty well sorted out. They depend on roughly the same libraries
anyway and it's way easier of the single library can both read and write
the capture files (along with bringing in libsysprof-capture symbols in
a single place).
This instrument does as our previous symbols_source did and will augment
the capture with additional symbols that improves the chances you'll get
proper symbolization on machines that did not create the capture.
