upgraded Sdk versions

gen-libs/build.gradle

@@ -1,18 +1,17 @@
 apply plugin: 'com.android.library'
 
 android {
-    compileSdkVersion 26
-    buildToolsVersion "26.0.1"
+    compileSdkVersion 25
 
     defaultConfig {
-        minSdkVersion 14
-        targetSdkVersion 17
+        minSdkVersion 21
+        targetSdkVersion 23
         versionCode 1
         versionName "1.0"
 
         externalNativeBuild {
             cmake {
-                arguments '-DANDROID_PLATFORM=android-17',
+                arguments '-DANDROID_PLATFORM=android-21',
                           '-DANDROID_TOOLCHAIN=clang'
                 // explicitly build libs
                 // targets 're', 'rem', 'baresip'
@@ -36,5 +35,5 @@ android {
 
 dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
-    compile 'com.android.support:appcompat-v7:23.4.0'
+    compile 'com.android.support:appcompat-v7:25.2.0'
 }