patch 8.2.2638: cannot write a message to the terminal from the GUI

Problem:    Cannot write a message to the terminal from the GUI.
Solution:   Add :echoconsole and use it in the test runner. (issue #7975)
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index 90fd015..aa41ab3 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -530,6 +530,9 @@
 EXCMD(CMD_echomsg,	"echomsg",	ex_execute,
 	EX_EXTRA|EX_NOTRLCOM|EX_SBOXOK|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_NONE),
+EXCMD(CMD_echoconsole,	"echoconsole",	ex_execute,
+	EX_EXTRA|EX_NOTRLCOM|EX_SBOXOK|EX_CMDWIN|EX_LOCK_OK,
+	ADDR_NONE),
 EXCMD(CMD_echon,	"echon",	ex_echo,
 	EX_EXTRA|EX_NOTRLCOM|EX_SBOXOK|EX_CMDWIN|EX_LOCK_OK,
 	ADDR_NONE),