refactor, libc made optional

Common/std.h

@@ -1,4 +1,20 @@
+/*
+    Minimal subset of stdlib, none of which have to be actually implemented,
+   even memory mnagement.
+*/
 
-/* TODO: Actually implement. */
-#define realloc(m_p, m_b) (NULL)
-#define free(m_p) ((void)0)
+#include <stdbool.h>
+#include <stddef.h>
+
+extern void *com_std_realloc(void *ptr, size_t size);
+extern void com_std_free(void *ptr);
+
+/* Note: Functions listed below are only available for test builds. */
+/* Trigonometry functions are for reference testing of our own fixed point
+ * implementations. Do not use otherwise. */
+extern void com_std_assert(bool holds);
+extern void com_std_printf(char const *fmt, ...);
+extern double com_std_sqrt(double v);
+extern double com_std_fabs(double v);
+extern double com_std_sin(double v);
+extern double com_std_cos(double v);