Added comparison benchmarks

# Conflicts:
#	benchmark/single-source/StringComparison.swift

Author: Lance Parker

benchmark/CMakeLists.txt

@@ -118,6 +118,7 @@ set(SWIFT_BENCH_MODULES
     single-source/StrComplexWalk
     single-source/StrToInt
     single-source/StringBuilder
+    single-source/StringComparison
     single-source/StringEdits
     single-source/StringEnum
     single-source/StringInterpolation