[dfsan] Abort at runtime on indirect calls to uninstrumented vararg functions.

We currently have no infrastructure to support these correctly.

This is accomplished by generating a call to a runtime library function that
aborts at runtime in place of the regular wrapper for such functions. Direct
calls are rewritten in the usual way during traversal of the caller's IR.

We also remove the "split-stack" attribute from such wrappers, as the code
generator cannot currently handle split-stack vararg functions.
[dfsan] Modify build-libc-list.py to filter out local functions in generated
ABI list.
[dfsan] Upgrade ABI list to Ubuntu 14.04.

This incorporates some of the newer functions used by (e.g.) the Go runtime.
[dfsan] Add libgo functions to ABI list.
[dfsan] Add runtime function for aborting on indirect calls to
uninstrumented vararg functions.