Small fixes as always, + add pi program

src/programs/pi.c

@@ -0,0 +1,34 @@
+// Program for Pi computation using Leibniz series
+// Author: xamidev
+// Licensed under the Unlicense. See the repo below.
+// https://github.com/xamidev/blankos
+
+#include "../libc/stdio.h"
+#include "../libc/string.h"
+
+void program_pi(int argc, char* argv[])
+{
+	if (argc < 2)
+	{
+		printf("Usage: %s <terms>\n", argv[0]);
+		return;
+	}
+
+	double pi = 0.0;
+	int terms = atoi(argv[1]);
+	
+	for (int i=0; i<terms; i++)
+	{
+		double term = 1.0/(2*i+1);
+		if (i%2 == 0)
+		{
+			pi += term;
+		} else {
+			pi -= term;
+		}
+	}
+
+	pi *= 4;
+
+	printf("%f\n", pi);
+}