Use fseek/ftell on Android when api level < 24

[davidoakley]

Android only supports fseeko+ftello (and their 64-bit versions) for API level 24 and above.

Tested using: cmake -Bbuild -DCMAKE_TOOLCHAIN_FILE=~/Library/Android/sdk/ndk/26.0.10792818/build/cmake/android.toolchain.cmake -DANDROID_ABI=armeabi-v7a -DANDROID_PLATFORM=android-22 . cmake --build build

Failed with: tinyxml2/tinyxml2.cpp:2380:5: error: use of undeclared identifier 'fseeko'; did you mean 'fseek'? .../Library/Android/sdk/ndk/26.0.10792818/toolchains/llvm/prebuilt/darwin-x86_64/sysroot/usr/include/stdio.h:215:5: note: 'fseek' declared here tinyxml2/tinyxml2.cpp:2390:44: error: use of undeclared identifier 'ftello'; did you mean 'ftell'? .../Library/Android/sdk/ndk/26.0.10792818/toolchains/llvm/prebuilt/darwin-x86_64/sysroot/usr/include/stdio.h:216:6: note: 'ftell' declared here