Sort "deps" and "public_deps" when running the "gn format" command.

tools/gn/format_test_data/063.gn

 source_set("test") {
+  a = "a"
   deps = [
-    "//c",
     "//a",
-    ":b",
-    "../d",
+    "//a/a",
+    "//a:a",
+    ":a",
+    "a",
+    a,

[Dirk Pranke, 2015/12/02 18:53:28]

This is definitely not right. I would think it should be:

deps = [
  ":a",
  "a",
  "//a",
  "//a:a",
  "//a/a",
  a,
]

though I could also see a case for moving the last line (the variable) elsewhere
in the ordering.

   ]
 
   public_deps = []
   if (condition) {
     public_deps += [
-      "//y",
-      "//w",
-      ":x",
-      "../z",
+      "//a",
+      "//a/a",
+      "//a:a",
+      ":a",
+      "a",
+      a,
     ]
   }
 }