cmd/gomobile: update the doc about the minimum Android SDK version

Change-Id: Ia17aadf683b8e3e918e0490b9b3bf4f6ae48d813
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/472236
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hajime Hoshi <hajimehoshi@gmail.com>

cmd/gomobile/doc.go

diff --git a/cmd/gomobile/doc.go b/cmd/gomobile/doc.go
index 10e3127..74090da 100644
--- a/cmd/gomobile/doc.go
+++ b/cmd/gomobile/doc.go
@@ -52,7 +52,7 @@
 the module import wizard (File > New > New Module > Import .JAR or
 .AAR package), and setting it as a new dependency
 (File > Project Structure > Dependencies).  This requires 'javac'
-(version 1.7+) and Android SDK (API level 15 or newer) to build the
+(version 1.7+) and Android SDK (API level 16 or newer) to build the
 library for Android. The environment variable ANDROID_HOME must be set
 to the path to Android SDK. Use the -javapkg flag to specify the Java
 package prefix for the generated classes.
@@ -113,7 +113,7 @@
 The default version is 13.0.
 
 Flag -androidapi sets the Android API version to compile against.
-The default and minimum is 15.
+The default and minimum is 16.
 
 The -bundleid flag is required for -target ios and sets the bundle ID to use
 with the app.
@@ -132,9 +132,9 @@
 
 	gomobile clean
 
-# Clean removes object files and cached NDK files downloaded by gomobile init
+Clean removes object files and cached NDK files downloaded by gomobile init.
 
-Build OpenAL for Android
+# Build OpenAL for Android
 
 Usage: