Add DTrace and Makefile dependency includes.

Sample file mpq.d by Georg Lukas; license GPL 2.
Sample file counts.d by Kate Turner; public domain.
Sample file javascript-race.d by unknown; license MPL 1.1/GPL 2.0/LGPL 2.1.
Sample file probes.d by momjian; license TBD.

lib/linguist/heuristics.rb

@@ -229,5 +229,15 @@ module Linguist
         Language["Text"]
       end
     end
+
+    disambiguate "D", "DTrace", "Makefile" do |data|
+      if /^module /.match(data)
+        Language["D"]
+      elsif /^((dtrace:::)?BEGIN|provider |#pragma (D (option|attributes)|ident)\s)/.match(data)
+        Language["DTrace"]
+      elsif /(\/.*:( .* \\)$| : \\$|^ : |: \\$)/.match(data)
+        Language["Makefile"]
+      end
+    end
   end
 end

lib/linguist/languages.yml

@@ -704,6 +704,15 @@ DM:
   tm_scope: source.c++
   ace_mode: c_cpp
 
+DTrace:
+  type: programming
+  extensions:
+  - .d
+  interpreters:
+  - dtrace
+  tm_scope: source.c
+  ace_mode: c_cpp
+
 Darcs Patch:
   type: programming
   search_term: dpatch
@@ -1753,6 +1762,7 @@ Makefile:
   - mf
   extensions:
   - .mak
+  - .d
   - .mk
   filenames:
   - GNUmakefile