patch 8.2.0943: displaying ^M or ^J depends on current buffer

Problem:    Displaying ^M or ^J depends on current buffer.
Solution:   Pass the displayed buffer to transchar(). (closes #6225)
diff --git a/src/proto/charset.pro b/src/proto/charset.pro
index c582a8c..d364b8e 100644
--- a/src/proto/charset.pro
+++ b/src/proto/charset.pro
@@ -5,8 +5,9 @@
 char_u *transstr(char_u *s);
 char_u *str_foldcase(char_u *str, int orglen, char_u *buf, int buflen);
 char_u *transchar(int c);
+char_u *transchar_buf(buf_T *buf, int c);
 char_u *transchar_byte(int c);
-void transchar_nonprint(char_u *buf, int c);
+void transchar_nonprint(buf_T *buf, char_u *charbuf, int c);
 void transchar_hex(char_u *buf, int c);
 int byte2cells(int b);
 int char2cells(int c);