Add SSE2 accelerated version of FileMap analysis.

Author: michaelwoerister

src/Cargo.lock

@@ -2779,6 +2779,7 @@ name = "syntax_pos"
 version = "0.0.0"
 dependencies = [
  "arena 0.0.0",
+ "cfg-if 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_data_structures 0.0.0",
  "scoped-tls 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "serialize 0.0.0",

src/libsyntax_pos/Cargo.toml

@@ -14,3 +14,4 @@ rustc_data_structures = { path = "../librustc_data_structures" }
 arena = { path = "../libarena" }
 scoped-tls = { version = "0.1.1", features = ["nightly"] }
 unicode-width = "0.1.4"
+cfg-if = "0.1.2"