patch 8.0.0229: local 'formatprg' option value leaks

Problem:    When freeing a buffer the local value of the 'formatprg' option is
            not cleared.
Solution:   Add missing change.

Author: brammool

src/buffer.c

@@ -2153,6 +2153,7 @@ free_buf_options(
 #if defined(FEAT_CRYPT)
     clear_string_option(&buf->b_p_cm);
 #endif
+    clear_string_option(&buf->b_p_fp);
 #if defined(FEAT_EVAL)
     clear_string_option(&buf->b_p_fex);
 #endif

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    229,
 /**/
     228,
 /**/