patch 9.0.2127: translation Makefiles can be improved

Problem:  translation Makefiles can be improved
Solution: Modified and extended po-related Makefiles and
          related files

closes: #13518

Signed-off-by: RestorerZ <restorer@mail2k.ru>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/po/big5corr.c b/src/po/big5corr.c
new file mode 100644
index 0000000..de8045e
--- /dev/null
+++ b/src/po/big5corr.c
@@ -0,0 +1,58 @@
+/*
+ * Simplistic program to correct Big5 inside strings.  When a trail byte is a
+ * backslash it needs to be doubled.
+ * Public domain.
+ */
+
+/*
+ * 06.11.23, added by Restorer:
+ * For more details, see:
+ * https://github.com/vim/vim/pull/3261
+ * https://github.com/vim/vim/pull/3476
+ * https://github.com/vim/vim/pull/12153
+ * (read all comments)
+ *
+ * I checked the workability on the list of backslash characters
+ * specified in zh_TW.UTF-8.po. It works.
+ * But it is better to have someone native speaker check it.
+ *
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+	int
+main(int argc, char **argv)
+{
+	char buffer[BUFSIZ];
+	char *p;
+
+	while (fgets(buffer, BUFSIZ, stdin) != NULL)
+	{
+		for (p = buffer; *p != 0; p++)
+		{
+			if (strncmp(p, "charset=utf-8", 13) == 0
+				|| strncmp(p, "charset=UTF-8", 13) == 0)
+			{
+				fputs("charset=BIG-5", stdout);
+				p += 12;
+			}
+			else if (strncmp(p, "# Original translations", 23) == 0)
+			{
+				fputs("# Generated from zh_TW.UTF-8.po, DO NOT EDIT.", stdout);
+				while (p[1] != '\n')
+					++p;
+			}
+			else
+			{
+				if (*(unsigned char *)p >= 0xA1)
+				{
+					putchar(*p++);
+					if (*p == '\\')
+						putchar(*p);
+				}
+				putchar(*p);
+			}
+		}
+	}
+}