scripts: Update restriction formula syntax

 - The restriction list parsing now reflects the changes at
   <https://wiki.debian.org/BuildProfileSpec> which were agreed upon
   in the bootstrap sprint 2014 in Paris.
 - Restriction lists are now restriction formulas.
 - Restriction formulas are given in disjunctive normal form expression:
       pkg <bar baz> <blub>
 - Removal of the implicit prefix/namespace mechanic.
 - Since there can be more than one <> block, the regex in
   parse_string() in Dpkg::Deps is now greedy.
 - Construct the profiles entry of the Packages-List field by converting
   the "<bar baz> <blub>" syntax into "bar,baz+blub".
 - Include a temporary compatibility mapping for the old way to write
   the Build-Profiles field in binary packages which can be removed once
   all affected source packages have moved to the new syntax.
 - Adjust testcases.

Closes: #760158



[guillem@debian.org:
 - Add a warning when using the old syntax in dpkg-source.
 - Move comments before the regexes, not besides them in dpkg-source.
 - Change from an xnor to == in evaluate_restriction_formula().
 - Move the Dpkg::Util import close to the other Dpkg imports.
 - Add test cases for the new parse_build_profiles() behavior. ]

Signed-off-by: Guillem Jover <guillem@debian.org>