Fix invalid-read when a managed proxy configuration fails.
Prepare some mock functions to test #9288.
Write unit tests for configure_proxy().
Modifications to transports.c for the unit tests to work.

Both 'managed_proxy_list' and 'unconfigured_proxies_n' are global
src/or/transports.c variables that are not initialized properly when
unit tests are run.
Update pt/configure_proxy until it stops segfaulting
Fix mixed declaration/statement warning
Merge branch 'bug9288_rebased'

Conflicts:
	src/test/test_pt.c