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>

src/util.cpp

@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: MIT */
+
+#include <ctype.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "util.hpp"
+
+#include "extern/utf8decoder.hpp"
+
+char const *printChar(int c)
+{
+	// "'A'" + '\0': 4 bytes
+	// "'\\n'" + '\0': 5 bytes
+	// "0xFF" + '\0': 5 bytes
+	static char buf[5];
+
+	if (c == EOF)
+		return "EOF";
+
+	if (isprint(c)) {
+		buf[0] = '\'';
+		buf[1] = c;
+		buf[2] = '\'';
+		buf[3] = '\0';
+		return buf;
+	}
+
+	switch (c) {
+	case '\n':
+		buf[2] = 'n';
+		break;
+	case '\r':
+		buf[2] = 'r';
+		break;
+	case '\t':
+		buf[2] = 't';
+		break;
+
+	default: // Print as hex
+		buf[0] = '0';
+		buf[1] = 'x';
+		snprintf(&buf[2], 3, "%02hhX", (uint8_t)c); // includes the '\0'
+		return buf;
+	}
+	buf[0] = '\'';
+	buf[1] = '\\';
+	buf[3] = '\'';
+	buf[4] = '\0';
+	return buf;
+}
+
+size_t readUTF8Char(uint8_t *dest, char const *src)
+{
+	uint32_t state = 0;
+	uint32_t codep;
+	size_t i = 0;
+
+	for (;;) {
+		if (decode(&state, &codep, src[i]) == 1)
+			return 0;
+
+		if (dest)
+			dest[i] = src[i];
+		i++;
+
+		if (state == 0)
+			return i;
+	}
+}