DependencyCollector: Add svn req for Linuxbrew

Fix error: You must: brew install svn

Author: sjackman

Library/Homebrew/dependency_collector.rb

@@ -158,6 +158,8 @@ def resource_dep(spec, tags)
       Dependency.new("bazaar", tags)
     when strategy <= CVSDownloadStrategy
       Dependency.new("cvs", tags) if MacOS.version >= :mavericks || !MacOS::Xcode.provides_cvs?
+    when strategy <= SubversionDownloadStrategy
+      SubversionRequirement.new(tags)
     when strategy < AbstractDownloadStrategy
       # allow unknown strategies to pass through
     else

Library/Homebrew/requirements.rb

@@ -135,3 +135,9 @@ class GitRequirement < Requirement
   default_formula "git"
   satisfy { Utils.git_available? }
 end
+
+class SubversionRequirement < Requirement
+  fatal true
+  default_formula "subversion"
+  satisfy { which "svn" }
+end