patch 8.0.0712: the terminal implementation is incomplete

Problem:    The terminal implementation is incomplete.
Solution:   Add the 'termkey' option.

src/option.c

@@ -258,6 +258,7 @@
 # define PV_COLE	OPT_WIN(WV_COLE)
 #endif
 #ifdef FEAT_TERMINAL
+# define PV_TK		OPT_WIN(WV_TK)
 # define PV_TMS		OPT_WIN(WV_TMS)
 #endif
 #ifdef FEAT_SIGNS
@@ -2779,6 +2780,15 @@ static struct vimoption options[] =
 #else
 			    (char_u*)NULL, PV_NONE,
 			    {(char_u *)FALSE, (char_u *)FALSE}
+#endif
+			    SCRIPTID_INIT},
+    {"termkey", "tk",	    P_STRING|P_ALLOCED|P_RWIN|P_VI_DEF,
+#ifdef FEAT_TERMINAL
+			    (char_u *)VAR_WIN, PV_TK,
+			    {(char_u *)"\x17", (char_u *)NULL}
+#else
+			    (char_u *)NULL, PV_NONE,
+			    {(char_u *)NULL, (char_u *)0L}
 #endif
 			    SCRIPTID_INIT},
     {"termsize", "tms",	    P_STRING|P_ALLOCED|P_RWIN|P_VI_DEF,
@@ -10681,6 +10691,7 @@ get_varp(struct vimoption *p)
 	case PV_COLE:   return (char_u *)&(curwin->w_p_cole);
 #endif
 #ifdef FEAT_TERMINAL
+	case PV_TK:     return (char_u *)&(curwin->w_p_tk);
 	case PV_TMS:    return (char_u *)&(curwin->w_p_tms);
 #endif
 

src/option.h

@@ -1131,6 +1131,7 @@ enum
     , WV_COLE
 #endif
 #ifdef FEAT_TERMINAL
+    , WV_TK
     , WV_TMS
 #endif
 #ifdef FEAT_CURSORBIND

src/structs.h

@@ -270,6 +270,8 @@ typedef struct
 # define w_p_scl w_onebuf_opt.wo_scl	/* 'signcolumn' */
 #endif
 #ifdef FEAT_TERMINAL
+    char_u	*wo_tk;
+#define w_p_tk w_onebuf_opt.wo_tk	/* 'termkey' */
     char_u	*wo_tms;
 #define w_p_tms w_onebuf_opt.wo_tms	/* 'termsize' */
 #endif

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    712,
 /**/
     711,
 /**/