first usable version of kernel and commands

After an year of hard work, this is a first "usable" version of Jehanne.

qa/kern/getpid.c

@@ -0,0 +1,51 @@
+/*
+ * This file is part of Jehanne.
+ *
+ * Copyright (C) 2016 Giacomo Tesio <giacomo@tesio.it>
+ *
+ * Jehanne is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * Jehanne is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Jehanne.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <u.h>
+#include <libc.h>
+
+void
+main(void)
+{
+	int pid;
+	char err[ERRMAX];
+
+	pid = getmainpid(); // this comes from exec() syscall
+
+	if(getpid() != pid){
+		print("FAIL: getpid() != getmainpid()\n");
+		exits("FAIL");
+	}
+	rfork(RFNOMNT);
+	if(getpid() != pid){
+		print("FAIL: rfork(RFNOMNT); getpid() != getmainpid()\n");
+		exits("FAIL");
+	}
+	rfork(RFNOMNT|RFCNAMEG);
+	if(getpid() != -1){
+		print("FAIL: rfork(RFNOMNT|RFCNAMEG)); getpid() != -1\n");
+		exits("FAIL");
+	}
+	rerrstr(err, ERRMAX);
+	if(strcmp("getpid: cannot open neither #c/pid nor /dev/pid", err)){
+		print("FAIL: rfork(RFNOMNT|RFCNAMEG)); getpid() set errstr '%s'\n", err);
+		exits("FAIL");
+	}
+
+	print("PASS\n");
+	exits("PASS");
+}