- Added Process.getPid() and Terminal.isTerminal().

- Added a test command-line app.

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

@@ -0,0 +1,5 @@
+package net.rubygrapefruit.platform.internal;
+
+public class PosixProcessFunctions {
+    public static native int getPid();
+}

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

@@ -0,0 +1,5 @@
+package net.rubygrapefruit.platform.internal;
+
+public class PosixTerminalFunctions {
+    public static native boolean isatty(int fildes);
+}