patch 8.0.0398: illegal memory access with "t"

Problem:    Illegal memory access with "t".
Solution:   Use strncmp() instead of memcmp(). (Dominique Pelle, closes #1528)

src/search.c

@@ -1693,12 +1693,9 @@ searchc(cmdarg_T *cap, int t_cmd)
 		    if (p[col] == c && stop)
 			break;
 		}
-		else
-		{
-		    if (memcmp(p + col, lastc_bytes, lastc_bytelen) == 0
+		else if (STRNCMP(p + col, lastc_bytes, lastc_bytelen) == 0
 								       && stop)
 		    break;
-		}
 		stop = TRUE;
 	    }
 	}

src/testdir/test_search.vim

@@ -294,3 +294,10 @@ func Test_searchpair()
   q!
 endfunc
 
+func Test_searchc()
+  " These commands used to cause memory overflow in searchc().
+  new
+  norm ixx
+  exe "norm 0t\u93cf"
+  bw!
+endfunc

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    398,
 /**/
     397,
 /**/