Gemfile: update rbpdf to version 1.18.2 (#18176)

git-svn-id: http://svn.redmine.org/redmine@13506 e93f8b46-1217-0410-a6f0-8f06a7374b81
Merged r13506 from trunk to 2.6-stable (#18176)

Gemfile: update rbpdf to version 1.18.2.

git-svn-id: http://svn.redmine.org/redmine@13507 e93f8b46-1217-0410-a6f0-8f06a7374b81
Code cleanup.

git-svn-id: http://svn.redmine.org/redmine@13508 e93f8b46-1217-0410-a6f0-8f06a7374b81
Makes Project#assignable_users return a scope that prevents 2*n queries.

git-svn-id: http://svn.redmine.org/redmine@13509 e93f8b46-1217-0410-a6f0-8f06a7374b81
Clear @assignable_users on reload.

git-svn-id: http://svn.redmine.org/redmine@13510 e93f8b46-1217-0410-a6f0-8f06a7374b81