Migrate a lot of C to C++.

It will let me put a lot more dtors into certain
structs that C++ code calls `free` on members within.

src/colors.hh

@@ -0,0 +1,18 @@
+#ifndef __COLORS_H__
+#define __COLORS_H__
+
+#include "config.h"
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+int32_t a_Color_parse (const char *str, int32_t default_color, int *err);
+int32_t a_Color_vc(int32_t candidate, int32_t c1, int32_t c2, int32_t c3);
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* __COLORS_H__ */