patch 8.2.0229: compare instructions not tested

Problem:    Compare instructions not tested.
Solution:   Add test cases.  Fix disassemble with line continuation.
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 0c72168..96037d9 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -2342,7 +2342,7 @@
 		emsg(_(e_missbrac));
 		return FAIL;
 	    }
-	    *arg = skipwhite(*arg + 1);
+	    *arg = *arg + 1;
 
 	    if (generate_instr_drop(cctx, ISN_INDEX, 1) == FAIL)
 		return FAIL;