Added SystemInfo and FileSystems to query system and file system information, respectively.

src/main/java/net/rubygrapefruit/platform/internal/PosixFileSystems.java

@@ -0,0 +1,21 @@
+package net.rubygrapefruit.platform.internal;
+
+import net.rubygrapefruit.platform.FileSystem;
+import net.rubygrapefruit.platform.FileSystems;
+import net.rubygrapefruit.platform.NativeException;
+import net.rubygrapefruit.platform.internal.jni.PosixFileSystemFunctions;
+
+import java.util.List;
+
+public class PosixFileSystems implements FileSystems {
+    @Override
+    public List<FileSystem> getFileSystems() {
+        FunctionResult result = new FunctionResult();
+        FileSystemList fileSystems = new FileSystemList();
+        PosixFileSystemFunctions.listFileSystems(fileSystems, result);
+        if (result.isFailed()) {
+            throw new NativeException(String.format("Could not query file systems: %s", result.getMessage()));
+        }
+        return fileSystems.fileSystems;
+    }
+}