first usable version of kernel and commands

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

qa/kern/mixedfloat.c

@@ -0,0 +1,33 @@
+#include <u.h>
+#include <libc.h>
+
+#define INT	2
+#define FLOAT	2.5
+#define A	4	// addition result
+#define M	5	// multiplication result
+
+void
+main()
+{
+	int a, b, x, y;
+	float f;
+	double d;
+
+	f = FLOAT;
+	d = FLOAT;
+	a = b = x = y = INT;
+
+	a += (double)d;
+	b *= (double)d;
+	x += (float)f;
+	y *= (float)f;
+
+	fprint(2, "[double] addition: %d; multiplication: %d\n", a, b);
+
+	fprint(2, "[float] addition: %d; multiplication: %d\n", x, y);
+
+	if(a != A || x != A || b != M || y != M)
+		exits("FAIL");
+	print("PASS\n");
+	exits("PASS");
+}