patch 8.0.1026: GTK on-the-spot input has problems

Problem:    GTK on-the-spot input has problems. (Gerd Wachsmuth)
Solution:   Support over-the-spot. (Yukihiro Nakadaira, Ketn Takata, closes
            #1215)
diff --git a/src/option.h b/src/option.h
index bfbea39..8f7255d 100644
--- a/src/option.h
+++ b/src/option.h
@@ -581,6 +581,9 @@
 EXTERN char_u	*p_imak;	/* 'imactivatekey' */
 EXTERN char_u	*p_imaf;	/* 'imactivatefunc' */
 EXTERN char_u	*p_imsf;	/* 'imstatusfunc' */
+EXTERN long	p_imst;		/* 'imstyle' */
+# define IM_ON_THE_SPOT		0L
+# define IM_OVER_THE_SPOT	1L
 #endif
 #ifdef USE_IM_CONTROL
 EXTERN int	p_imcmdline;	/* 'imcmdline' */