Converted the REDMINE_SUPPORTED_SCM constant to a class

Now SCMs can be added or removed using a simple API, instead of being
hardcoded:

  Redmine::Scm::Base.add('ScmName')
  Redmine::Scm::Base.delete('ScmName')

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@3440 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/redmine.rb

@@ -7,6 +7,7 @@ require 'redmine/themes'
 require 'redmine/hook'
 require 'redmine/plugin'
 require 'redmine/wiki_formatting'
+require 'redmine/scm/base'
 
 begin
   require_library_or_gem 'RMagick' unless Object.const_defined?(:Magick)
@@ -21,7 +22,13 @@ else
   FCSV = CSV
 end
 
-REDMINE_SUPPORTED_SCM = %w( Subversion Darcs Mercurial Cvs Bazaar Git Filesystem )
+Redmine::Scm::Base.add "Subversion"
+Redmine::Scm::Base.add "Darcs"
+Redmine::Scm::Base.add "Mercurial"
+Redmine::Scm::Base.add "Cvs"
+Redmine::Scm::Base.add "Bazaar"
+Redmine::Scm::Base.add "Git"
+Redmine::Scm::Base.add "Filesystem"
 
 # Permissions
 Redmine::AccessControl.map do |map|