general update, updated cimport so it parses struct definitions from imported headers, improved the error reporting, added ifdef and ifndef, added proper support for extern variadic functions, added some new sections and pages to the doc tool and added --check to only check the program corectness and run compile time defs without producing a binary

tests/variadic_extern.sl

@@ -0,0 +1,34 @@
+import stdlib.sl
+
+# Test variadic extern declarations.
+# For variadic externs, the TOS literal before the call is the number of
+# extra variadic arguments.  The compiler consumes it (not passed to C).
+# String literals push (ptr, len) — use drop to discard the length for C.
+
+# printf: 1 fixed param (fmt), variadic args via TOS count
+extern int printf(const char *fmt, ...)
+extern int fflush(long stream)
+
+# Custom C variadic: sums args until sentinel -1 is seen
+extern long va_sum_sentinel(long first, ...)
+
+# Non-variadic extern for comparison
+extern long add_two(long a, long b)
+
+word main
+    # Test 1: non-variadic add_two
+    10 20 add_two puti cr
+
+    # Test 2: printf with 0 variadic args (just format string)
+    "hello\n" drop 0 printf drop
+    0 fflush drop
+
+    # Test 3: printf with 2 variadic args
+    "%d %d\n" drop 42 99 2 printf drop
+    0 fflush drop
+
+    # Test 4: va_sum_sentinel(10, 20, 30, -1) = 60
+    10 20 30 -1 3 va_sum_sentinel puti cr
+
+    0
+end