patch 8.2.2982: Vim9: future commands are not reserved yet

Problem:    Vim9: future commands are not reserved yet.
Solution:   Add commands to be implemented later.  Make "this" a reserved
            name.
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index 8a1ed5e..8ddac37 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -122,6 +122,9 @@
 EXCMD(CMD_aboveleft,	"aboveleft",	ex_wrongmodifier,
 	EX_NEEDARG|EX_EXTRA|EX_NOTRLCOM,
 	ADDR_NONE),
+EXCMD(CMD_abstract,	"abstract",	ex_ni,
+	EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
+	ADDR_NONE),
 EXCMD(CMD_all,		"all",		ex_all,
 	EX_BANG|EX_RANGE|EX_COUNT|EX_TRLBAR,
 	ADDR_OTHER),
@@ -551,6 +554,9 @@
 EXCMD(CMD_endif,	"endif",	ex_endif,
 	EX_TRLBAR|EX_SBOXOK|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_NONE),
+EXCMD(CMD_endinterface,	"endinterface",	ex_ni,
+	EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
+	ADDR_NONE),
 EXCMD(CMD_endclass,	"endclass",	ex_ni,
 	EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_NONE),
@@ -734,6 +740,9 @@
 EXCMD(CMD_intro,	"intro",	ex_intro,
 	EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_NONE),
+EXCMD(CMD_interface,	"interface",	ex_ni,
+	EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
+	ADDR_NONE),
 EXCMD(CMD_isearch,	"isearch",	ex_findpat,
 	EX_BANG|EX_RANGE|EX_DFLALL|EX_WHOLEFOLD|EX_EXTRA|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_LINES),
@@ -1463,6 +1472,9 @@
 EXCMD(CMD_startreplace,	"startreplace",	ex_startinsert,
 	EX_BANG|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_NONE),
+EXCMD(CMD_static,	"static",	ex_ni,
+	EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
+	ADDR_NONE),
 EXCMD(CMD_stopinsert,	"stopinsert",	ex_stopinsert,
 	EX_BANG|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_NONE),