Set default backlog_lines = 0 (fixes Debian bug #818374)

This would have defaults move to backlog_always=false / log=true /
backlog_lines=0, which should not cause much trouble as backlog will
be reset after being displayed.

Also, it is doubtfuk anyone would be keeping the default of 10 for
backlog as it is pretty much an undesirable configuration.

We need to annouce this change as important though, so users having
log = false are aware memory usage could increase if they don't set
it manually to another value.

Signed-off-by: Loïc Gomez <bip@animanova.fr>

Makefile.am

@@ -3,7 +3,7 @@ if COND_WANT_TESTS
 endif
 SUBDIRS = src . $(MAYBE_TESTS)
 
-dist_man_MANS = bip.1 bip.conf.5 bipmkpw.1 bipgenconfig.1
+dist_man_MANS = bip.1 bip.conf.5 bipmkpw.1
 
 examplesdir = $(prefix)/share/doc/bip/examples/
 dist_examples_DATA = samples/bip.conf samples/bip.vim