* src/log.c: turn on automatic format check for log_vprintf_internal()
 * Test-proxied-https-auth.px:
   add valgrind support,
   sync parent / child (client / server)

Fixed the missing synchronization between server and client.
Without this, we experienced random test failures.
Also added valgrind support.
 * added new test Test-proxied-https-auth-keepalive.px

 This test similar to Test-proxied-https-auth except that his test
 simulates a persistent connection to the destination server.
 * WgetFeature.pm: Fixed finding of WgetFeature.cfg when using separate
   build dirs.
 * WgetFeature.pm: Fixed warning from BLOCK eval, made it indo EXPR eval

This fixes 'make distcheck' and removes a warning.
 * iri.c (remote_to_utf8): Fixed assumption that char is signed.

Fixes fellowing test case failures idn-cmd-utf8, idn-robots-utf8,
if char is unsigned.