Port linkerscript parser to Bison (#1266)

Notable side effects:
* Use the standard-conformant MSVC preproc
* Add test for linker script INCLUDE
* Improve wording of placement conflict errors
* Fix errors from not newline-terminated files
* Teach checkdiff about the linker script doc
* Call linker script "commands" "directives" instead

---------

Co-authored-by: Rangi42 <remy.oukaour+rangi42@gmail.com>

include/util.hpp

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: MIT */
+
+#ifndef RGBDS_UTIL_H
+#define RGBDS_UTIL_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+char const *printChar(int c);
+
+/*
+ * @return The number of bytes read, or 0 if invalid data was found
+ */
+size_t readUTF8Char(uint8_t *dest, char const *src);
+
+#endif // RGBDS_UTIL_H