Spring cleaning is here! In the Fall! This commit removes quite a large amount
of deprecated functionality from the standard libraries. I tried to ensure that
only old deprecated functionality was removed.
This is removing lots and lots of deprecated features, so this is a breaking
change. Please consult the deprecation messages of the deleted code to see how
to migrate code forward if it still needs migration.
[breaking-change]
This involved a few changes to the local build system:
* Makefiles now prefer our own LD_LIBRARY_PATH over the user's LD_LIBRARY_PATH
in order to support building rust with rust already installed.
* The compiletest program was taught to correctly pass through the aux dir as a
component of LD_LIBRARY_PATH in more situations.
This change was spliced out of #14832 to consist of just the fixes to running
tests without an rpath setting embedded in executables.
