refactor, libc made optional

Common/Std/libc.c

@@ -0,0 +1,20 @@
+#include "../std.h"
+#include <assert.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <tgmath.h>
+
+void *com_std_realloc(void *ptr, size_t size) { return realloc(ptr, size); }
+void com_std_free(void *ptr) { free(ptr); }
+void com_std_assert(bool holds) { assert(holds); }
+void com_std_printf(char const *fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+  vprintf(fmt, args);
+  va_end(args);
+}
+double com_std_sqrt(double v) { return sqrt(v); }
+double com_std_fabs(double v) { return fabs(v); }
+double com_std_sin(double v) { return sin(v); }
+double com_std_cos(double v) { return cos(v); }

Common/Std/stub.c

@@ -0,0 +1,10 @@
+#include "../std.h"
+
+void *com_std_realloc(void *ptr, size_t size) { return NULL; }
+void com_std_free(void *ptr) {}
+void com_std_assert(bool holds) {}
+void com_std_printf(char const *fmt, ...) {}
+double com_std_sqrt(double v) { return 0; }
+double com_std_fabs(double v) { return 0; }
+double com_std_sin(double v) { return 0; }
+double com_std_cos(double v) { return 0; }