increment version number to 0.20.18

NEWS

+ver 0.20.18 (not yet released)
+
 ver 0.20.17 (2018/02/11)
 * output
   - alsa: fix crash bug with 8 channels

android/AndroidManifest.xml

@@ -2,8 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           package="org.musicpd"
           android:installLocation="auto"
-          android:versionCode="16"
-          android:versionName="0.20.17">
+          android:versionCode="17"
+          android:versionName="0.20.18">
 
   <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="17"/>
 

configure.ac

 AC_PREREQ(2.60)
 
-AC_INIT(mpd, 0.20.17, musicpd-dev-team@lists.sourceforge.net)
+AC_INIT(mpd, 0.20.18, musicpd-dev-team@lists.sourceforge.net)
 
 VERSION_MAJOR=0
 VERSION_MINOR=20
-VERSION_REVISION=17
+VERSION_REVISION=18
 VERSION_EXTRA=0
 
 AC_CONFIG_SRCDIR([src/Main.cxx])