better error reporting when futzing with inferior allocations.
bfd: add 'rt' as a library to be sure we import.
we never care about memory from "opal_malloc".
user mem: provide early out for 'calloc' symbols.

glibc apparently has an internal "__libc_calloc" symbol, which we
would end up ignoring due to our skipping of all "internal"
symbols (i.e. symbols that begin with a "__").
bfd: large cleanup.

* use my 'msg' channels instead of custom crap that requires
  hacking source.
* generate a list of libraries to load and iterate through them
  separately.
* use Go1.4's "ImportedSymbols" to filter out some irrelevant
  syms.
* simplify logic for 'accept no imitations' symbols.
fix comment
user_symbol: fix comment, plus ignore OpenMPI functions.