requirements: recommend casks where available.

Also, tweak the XQuartz requirement to not show 0.0.0 versions being required.

Closes Homebrew/homebrew#35254.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Library/Homebrew/requirements.rb

@@ -73,7 +73,10 @@ class TeXDependency < Requirement
     <<-EOS.undent
     A LaTeX distribution is required for Homebrew to install this formula.
 
-    You can install MacTeX distribution from:
+    You can install MacTeX distribution with:
+      brew cask install mactex
+
+    Or from:
       http://www.tug.org/mactex/
 
     Make sure that "/usr/texbin", or the location you installed it to, is in
@@ -136,10 +139,11 @@ class JavaDependency < Requirement
     <<-EOS.undent
       Java#{version_string} is required to install this formula.
 
-      You can install Java from:
+      You can install the Java Development Kit (JDK) with:
-        http://www.oracle.com/technetwork/java/javase/downloads/index.html
+        brew cask install java
 
-      Make sure you install both the JRE and JDK.
+      Or from:
+        http://www.oracle.com/technetwork/java/javase/downloads/index.html
     EOS
   end
 end

Library/Homebrew/requirements/x11_dependency.rb

@@ -12,8 +12,10 @@ class X11Dependency < Requirement
     @name = name
     if /(\d\.)+\d/ === tags.first
       @min_version = Version.new(tags.shift)
+      @min_version_string = " #{@min_version}"
     else
       @min_version = Version.new("0.0.0")
+      @min_version_string = ""
     end
     super(tags)
   end
@@ -23,8 +25,10 @@ class X11Dependency < Requirement
   end
 
   def message; <<-EOS.undent
-    Unsatisfied dependency: XQuartz #{@min_version}
+    You can install XQuartz#{@min_version_string} with:
-    Homebrew does not package XQuartz. Installers may be found at:
+      brew cask install xquartz
+
+    Or from:
       https://xquartz.macosforge.org
     EOS
   end