Updated Android API level to 24

Fixes build errors in libcurl with NDK r26 due to fseeko not being available in NDK r23 on armeabi-v7a.

Fixes #17.

README.md

@@ -5,7 +5,7 @@ GNUstep Android Toolchain
 
 This project comprises a collection of scripts to build a GNUstep toolchain for Android. The toolchain can then be used in an Android project to compile and run Objective-C code using the Foundation and CoreFoundation libraries.
 
-The toolchain is built using the Android NDK (installed e.g. via [Android Studio](https://developer.android.com/studio)), and is set up to target Android API level 23 (6.0 / Marshmallow) and all common Android ABIs (armeabi-v7a, arm64-v8a, x86, x86_64).
+The toolchain is built using the Android NDK (installed e.g. via [Android Studio](https://developer.android.com/studio)), and is set up to target Android API level 24 (7.0 / Nougat) and all available Android ABIs (armeabi-v7a, arm64-v8a, x86, x86_64).
 
 
 Libraries

scripts/sdkenv.sh

@@ -22,7 +22,7 @@ esac
 # Target (allow overrides)
 ABI_NAMES=${ABI_NAMES:-armeabi-v7a arm64-v8a x86 x86_64}
 ABI_NAME=${ABI_NAME:-armeabi-v7a}
-ANDROID_API_LEVEL=${ANDROID_API_LEVEL:-23}
+ANDROID_API_LEVEL=${ANDROID_API_LEVEL:-24}
 BUILD_TYPE=${BUILD_TYPE:-RelWithDebInfo}
 
 # ABI-dependant properties