patch 8.1.0125: virtual edit replace with multi-byte fails at end of line

Problem:    Virtual edit replace with multi-byte fails at end of line. (Lukas
            Werling)
Solution:   use ins_char() to add the character. (Christian Brabandt,
            closes #3114)  Rename PCHAR() to PBYTE() to avoid mistakes like
            this.

src/testdir/test_virtualedit.vim

@@ -42,6 +42,22 @@ func Test_paste_end_of_line()
   set virtualedit=
 endfunc
 
+func Test_replace_end_of_line()
+  new
+  set virtualedit=all
+  call setline(1, range(20))
+  exe "normal! gg2jv10lr-"
+  call assert_equal(["1", "-----------", "3"], getline(2,4))
+  if has('multi_byte')
+    call setline(1, range(20))
+    exe "normal! gg2jv10lr\<c-k>hh"
+    call assert_equal(["1", "───────────", "3"], getline(2,4))
+  endif
+
+  bwipe!
+  set virtualedit=
+endfunc
+
 func Test_edit_CTRL_G()
   new
   set virtualedit=insert