Rename walkLiteral method to more explicitly say what it does

src/Composer/DependencyResolver/RuleWatchGraph.php

@@ -43,7 +43,7 @@ class RuleWatchGraph
         return isset($this->watches[$literal]);
     }
 
-    public function walkLiteral($literal, $level, $skipCallback, $conflictCallback, $decideCallback)
+    public function propagateLiteral($literal, $level, $skipCallback, $conflictCallback, $decideCallback)
     {
         if (!isset($this->watches[$literal])) {
             return null;

src/Composer/DependencyResolver/Solver.php

@@ -318,7 +318,7 @@ class Solver
 
             $this->propagateIndex++;
 
-            $conflict = $this->watchGraph->walkLiteral(
+            $conflict = $this->watchGraph->propagateLiteral(
                 $literal,
                 $level,
                 array($this, 'decisionsContain'),