v0.7.0: adjusted proguard config, as the optimize variant is becoming default

core/build.gradle

@@ -17,7 +17,7 @@ android {
         release {
             shrinkResources true
             minifyEnabled true
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
         }
     }
 }

core/proguard-rules.pro

@@ -3,4 +3,9 @@
 -keepnames class com.watabou.** { *; }
 -keep class com.shatteredpixel.shatteredpixeldungeon { *; }
 -keep class com.watabou.noosa.game { *; }
--keepattributes SourceFile,LineNumberTable
+-keepattributes SourceFile,LineNumberTable
+
+# overrides default in proguard-android-optimize.txt, which is:
+# -optimizations !code/simplification/arithmetic,!code/simplification/cast,!field/*,!class/merging/*
+# This is because code/simplification/arithmetic is safe to use on android 2.0+
+-optimizations !code/simplification/cast,!field/*,!class/merging/*