patch 8.1.1256: cannot navigate through errors relative to the cursor

Problem:    Cannot navigate through errors relative to the cursor.
Solution:   Add :cabove, :cbelow, :labove and :lbelow. (Yegappan Lakshmanan,
            closes #4316)
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index 63196af..7391472 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -252,6 +252,9 @@
 EX(CMD_cabclear,	"cabclear",	ex_abclear,
 			EXTRA|TRLBAR|CMDWIN,
 			ADDR_NONE),
+EX(CMD_cabove,		"cabove",	ex_cbelow,
+			RANGE|TRLBAR,
+			ADDR_OTHER),
 EX(CMD_caddbuffer,	"caddbuffer",	ex_cbuffer,
 			RANGE|WORD1|TRLBAR,
 			ADDR_OTHER),
@@ -270,6 +273,9 @@
 EX(CMD_cbuffer,		"cbuffer",	ex_cbuffer,
 			BANG|RANGE|WORD1|TRLBAR,
 			ADDR_OTHER),
+EX(CMD_cbelow,		"cbelow",	ex_cbelow,
+			RANGE|TRLBAR,
+			ADDR_OTHER),
 EX(CMD_cbottom,		"cbottom",	ex_cbottom,
 			TRLBAR,
 			ADDR_NONE),
@@ -726,6 +732,9 @@
 EX(CMD_last,		"last",		ex_last,
 			EXTRA|BANG|EDITCMD|ARGOPT|TRLBAR,
 			ADDR_NONE),
+EX(CMD_labove,		"labove",	ex_cbelow,
+			RANGE|TRLBAR,
+			ADDR_OTHER),
 EX(CMD_language,	"language",	ex_language,
 			EXTRA|TRLBAR|CMDWIN,
 			ADDR_NONE),
@@ -744,6 +753,9 @@
 EX(CMD_lbuffer,		"lbuffer",	ex_cbuffer,
 			BANG|RANGE|WORD1|TRLBAR,
 			ADDR_OTHER),
+EX(CMD_lbelow,		"lbelow",	ex_cbelow,
+			RANGE|TRLBAR,
+			ADDR_OTHER),
 EX(CMD_lbottom,		"lbottom",	ex_cbottom,
 			TRLBAR,
 			ADDR_NONE),