quite a few fixes, overall repo cleanup and some restructurization in the stdlib

c_extern.sl

@@ -1,13 +1,22 @@
-import stdlib/io.sl
+import stdlib.sl
+import float.sl
 
 # C-style externs (auto ABI handling)
 extern long labs(long n)
 extern void exit(int status)
+extern double atan2(double y, double x)
 
 word main
     # Test C-style extern with implicit ABI handling
     -10 labs puti cr
+
+    # Basic math
+    1.5 2.5 f+ fputln       # Outputs: 4.000000
     
+    # External math library (libm)
+    10.0 10.0 atan2         # Result is pi/4
+    4.0 f* fputln           # Outputs: 3.141593 (approx pi)
+
     # Test extern void
     0 exit
 end