sh: Fix some dead stores.

Found by:	clang static analyzer

bin/sh/expand.c

@@ -463,7 +463,6 @@ expbackq(union node *cmd, int quoted, int flag, struct worddest *dst)
 	argbackq = saveargbackq;
 
 	p = in.buf;
-	lastc = '\0';
 	nnl = 0;
 	if (!quoted && flag & EXP_SPLIT)
 		ifs = ifsset() ? ifsval() : " \t\n";
@@ -1288,7 +1287,7 @@ patmatch(const char *pattern, const char *string)
 				if (wc == 0)
 					goto backtrack;
 			} else
-				wc = (unsigned char)*q++;
+				q++;
 			break;
 		case '*':
 			c = *p;

bin/sh/histedit.c

@@ -359,7 +359,7 @@ histcmd(int argc, char **argv __unused)
 					 * cursor, set it back to the current
 					 * entry.
 					 */
-					retval = history(hist, &he,
+					history(hist, &he,
 					    H_NEXT_EVENT, oldhistnum);
 				}
 			} else