patch 8.2.1548: cannot move position of "%%" in message translations

Problem:    Cannot move position of "%%" in message translations. (Emir Sarı)
Solution:   Improve the check script.

Author: brammool

src/po/check.vim

@@ -22,6 +22,7 @@ func! GetMline()
 
   " remove '%', not used for formatting.
   let idline = substitute(idline, "'%'", '', 'g')
+  let idline = substitute(idline, "%%", '', 'g')
 
   " remove '%' used for plural forms.
   let idline = substitute(idline, '\\nPlural-Forms: .\+;\\n', '', '')

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1548,
 /**/
     1547,
 /**/