cmd/compilebench: update list of packages

There's a surprising amount of variety
in the drivers of compilation speed.
It's helpful to have a variety of packages here.
For example, archive/tar exhibits golang/go#19839
much more than the others.

Change-Id: If66b332d63427fb246305cb14cfee9ef450bcdcf
Reviewed-on: https://go-review.googlesource.com/39713
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

compilebench/main.go

@@ -103,6 +103,12 @@ var tests = []struct {
 	{"BenchmarkUnicode", "unicode", false},
 	{"BenchmarkGoTypes", "go/types", false},
 	{"BenchmarkCompiler", "cmd/compile/internal/gc", false},
+	{"BenchmarkSSA", "cmd/compile/internal/ssa", false},
+	{"BenchmarkFlate", "compress/flate", false},
+	{"BenchmarkGoParser", "go/parser", false},
+	{"BenchmarkReflect", "reflect", false},
+	{"BenchmarkTar", "archive/tar", false},
+	{"BenchmarkXML", "encoding/xml", false},
 	{"BenchmarkMakeBash", "", true},
 	{"BenchmarkHelloSize", "", false},
 	{"BenchmarkCmdGoSize", "", true},