Tidy a few snippets: wrap+strip wide lines.
Fix python-distutils.mk and python-sugar.mk to use unversioned runtime for default flavor (see bug#377964).
Fix have perl-build.mk more aggressively detect use of Module::Build::Tiny.
Fix build Perl modules more verbosely. Introduce new variable DEB_MAKEMAKER_NORMAL_ARGS. Thanks to intrigeri.
Fix set LDFLAGS in perl-makemaker.mk.
Drop legacy flag handling from langcore.mk and drop unused variable DEB_OPT_FLAG: dpkg-buildflags is used instead when available (since cdbs 0.4.90), which is now the case even in oldstable.
Fix cdbs_set_nondefaultvars in buildvars.mk to skip undefined variables. Drop unused variable cdbs_set_nondefaultvar.

Dropped variable verified against <http://codesearch.debian.net>.
Tidy langcore.mk: Use cdbs_set_nondefaultvars to set buildflags in dpkg-buildflags call.
Speedup buildflags resolving: call dpkg-buildflags only once.
Fix buildflags resolving in langcore.mk to only pass documented supported environemnt variables to dpkg-buildflags (other DEB_* variables may be unsafe for simple shell-quoting.
Prepare for release: Update changelog.