Allow using internal popupmenu or ext_popupmenu for wildmenu

Deprecate ext_wildmenu. ext_popupmenu already contains more state (anchor
position), and will allow further expansion (info about items).

src/nvim/option_defs.h

@@ -659,6 +659,12 @@ extern char_u   *p_vfile;       /* 'verbosefile' */
 #endif
 EXTERN int p_warn;              // 'warn'
 EXTERN char_u   *p_wop;         // 'wildoptions'
+EXTERN unsigned wop_flags;
+# ifdef IN_OPTION_C
+static char *(p_wop_values[]) =  { "tagfile", "pum", NULL };
+#endif
+#define WOP_TAGFILE             0x01
+#define WOP_PUM                 0x02
 EXTERN long p_window;           // 'window'
 EXTERN char_u   *p_wak;         // 'winaltkeys'
 EXTERN char_u   *p_wig;         // 'wildignore'