Don't print 168^W143 lines of help when someone makes a typo.

Print actual usage messages in most cases.

Add --help and --version.

Bug: http://b/28054087
Test: manual
Change-Id: I39c1cb7a84f52e0c35d24f140ec55c3a181283fb
diff --git a/adb_utils.h b/adb_utils.h
index 16317e0..2b59034 100644
--- a/adb_utils.h
+++ b/adb_utils.h
@@ -21,6 +21,8 @@
 
 #include <android-base/macros.h>
 
+int usage(const char*, ...);
+
 void close_stdin();
 
 bool getcwd(std::string* cwd);