Update syn to 0.11

The last remnants of syn 0.10 are due to the WR stack still using serde_codegen to build on stable, but that isn't actually used in servo.
servo · bors-servo · Feb 27, 2017 · Feb 27, 2017 · Feb 27, 2017 · Feb 27, 2017
commit 626e212fcb3cbf98dad6943af5163664c09615fb
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/components/deny_public_fields/Cargo.toml b/components/deny_public_fields/Cargo.toml
@@ -10,5 +10,5 @@ path = "lib.rs"
 proc-macro = true
 
 [dependencies]
-syn = "0.10"
-synstructure = "0.4"
+syn = "0.11"
+synstructure = "0.5"
diff --git a/components/domobject_derive/Cargo.toml b/components/domobject_derive/Cargo.toml
@@ -10,5 +10,5 @@ path = "lib.rs"
 proc-macro = true
 
 [dependencies]
-syn = "0.10"
+syn = "0.11"
 quote = "0.3"
diff --git a/components/jstraceable_derive/Cargo.toml b/components/jstraceable_derive/Cargo.toml
@@ -10,6 +10,6 @@ path = "lib.rs"
 proc-macro = true
 
 [dependencies]
-syn = "0.10"
 quote = "0.3"
-synstructure = "0.4"
+syn = "0.11"
+synstructure = "0.5"