Refactor logic to remove trailing CR/LF characters from strings

b654714 has reworked the way trailing CR/LF characters are removed from
strings.  This commit introduces a new routine in common/string.c and
refactors the code so as the logic is in a single place, mostly.

Author: Michael Paquier
Reviewed-by: Bruce Momjian
Discussion: https://postgr.es/m/20190801031820.GF29334@paquier.xyz

src/common/string.c

@@ -90,3 +90,25 @@ pg_clean_ascii(char *str)
 			*p = '?';
 	}
 }
+
+
+/*
+ * pg_strip_crlf -- Remove any trailing newline and carriage return
+ *
+ * Removes any trailing newline and carriage return characters (\r on
+ * Windows) in the input string, zero-terminating it.
+ *
+ * The passed in string must be zero-terminated.  This function returns
+ * the new length of the string.
+ */
+int
+pg_strip_crlf(char *str)
+{
+	int			len = strlen(str);
+
+	while (len > 0 && (str[len - 1] == '\n' ||
+					   str[len - 1] == '\r'))
+		str[--len] = '\0';
+
+	return len;
+}