Merged r13354 from trunk to 2.4-stable

add Ruby 1.9.2 to .travis.yml

git-svn-id: http://svn.redmine.org/redmine@13356 e93f8b46-1217-0410-a6f0-8f06a7374b81
ensure issue pdf test has relations (#17570)

git-svn-id: http://svn.redmine.org/redmine@13357 e93f8b46-1217-0410-a6f0-8f06a7374b81
use rbpdf gem instead of bundled rfpdf (#17570)

Contributed by Jun NAITOH.

git-svn-id: http://svn.redmine.org/redmine@13358 e93f8b46-1217-0410-a6f0-8f06a7374b81
remove general_pdf_encoding from lib/redmine/export/pdf.rb (#17570)

git-svn-id: http://svn.redmine.org/redmine@13359 e93f8b46-1217-0410-a6f0-8f06a7374b81
remove general_pdf_encoding from locale yamls (#17570)

git-svn-id: http://svn.redmine.org/redmine@13360 e93f8b46-1217-0410-a6f0-8f06a7374b81