patch 8.0.0179: cannot have a local value for 'formatprg'

Problem:    'formatprg' is a global option but the value may depend on the
            type of buffer. (Sung Pae)
Solution:   Make 'formatprg' global-local. (closes #1380)
diff --git a/src/structs.h b/src/structs.h
index 3fdfb5f..9c0e046 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -2097,6 +2097,7 @@
     long_u	b_p_inde_flags;	/* flags for 'indentexpr' */
     char_u	*b_p_indk;	/* 'indentkeys' */
 #endif
+    char_u	*b_p_fp;	/* 'formatprg' */
 #if defined(FEAT_EVAL)
     char_u	*b_p_fex;	/* 'formatexpr' */
     long_u	b_p_fex_flags;	/* flags for 'formatexpr' */