protogen: generate message skeletons

Copy generator.CamelCase for camel-casing names, with one change: Convert
'.' in names to '_'. This removes the need for the CamelCaseSlice function
which operates on a []string representing a name split along '.'s.

Add protogen.Message.

Reformat generated code.

Add regenerate.bash, largely copied from regenerate.sh.

Change-Id: Iecf0bfc43b552f53e458499a328b933b0c9c5f82
Reviewed-on: https://go-review.googlesource.com/130915
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
diff --git a/protogen/names_test.go b/protogen/names_test.go
new file mode 100644
index 0000000..021e71a
--- /dev/null
+++ b/protogen/names_test.go
@@ -0,0 +1,33 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package protogen
+
+import "testing"
+
+func TestCamelCase(t *testing.T) {
+	tests := []struct {
+		in   string
+		want GoIdent
+	}{
+		{"one", "One"},
+		{"one_two", "OneTwo"},
+		{"_my_field_name_2", "XMyFieldName_2"},
+		{"Something_Capped", "Something_Capped"},
+		{"my_Name", "My_Name"},
+		{"OneTwo", "OneTwo"},
+		{"_", "X"},
+		{"_a_", "XA_"},
+		{"one.two", "One_Two"},
+		{"one_two.three_four", "OneTwo_ThreeFour"},
+		{"_one._two", "XOne_XTwo"},
+		{"SCREAMING_SNAKE_CASE", "SCREAMING_SNAKE_CASE"},
+		{"double__underscore", "Double_Underscore"},
+	}
+	for _, tc := range tests {
+		if got := camelCase(tc.in); got != tc.want {
+			t.Errorf("CamelCase(%q) = %q, want %q", tc.in, got, tc.want)
+		}
+	}
+}