always include config.h first

Solaris (and others?) need defines from it (GNU_SOURCE in particular)
Double allocated varnishlog buffer space.

Extensive test cases often lead to a lot of log output,
which at times tripped the following assert:

Assert error in vtc_log_emit(), vtc_log.c line 122:
  Condition(vtclog_left > l) not true.

Double the amount of buffer space allowed to avoid this. Another 256KB
memory use per concurrent running test should be fine.
Add that empty string VCL truth value changed.

Solves:		#1406
EL7 chroot seem not to have python by default.
recommend system libjemalloc
Prepare 3.0.6rc2.
Forgotten version number in last commit.
Improve description of effects of bug 1470.

Spotted by:	scoof
Update copyright statement.
Prepare 3.0.6.
Merge remote-tracking branch 'upstream/3.0' into 3.0.6-plus

Conflicts:
	configure.ac
	redhat/varnish.spec

Change-Id: I63a334c6c03fa9dc10a87afc4e21baab85dc0e80