toolbox: turn on -Werror

- Deal with some signedness issues
- Deal with some size issues
- Deal with NULL pointer issues
- Deal with some -Wunused issues

Change-Id: I1479dd90d690084491bae3475f2c547833519a57
diff --git a/toolbox/grep/file.c b/toolbox/grep/file.c
index 86b7658..d28dff5 100644
--- a/toolbox/grep/file.c
+++ b/toolbox/grep/file.c
@@ -78,7 +78,9 @@
 grep_refill(struct file *f)
 {
 	ssize_t nr;
+#ifndef ANDROID
 	int bzerr;
+#endif
 
 	bufpos = buffer;
 	bufrem = 0;
diff --git a/toolbox/grep/grep.c b/toolbox/grep/grep.c
index 5a4fa0c..7b2c487 100644
--- a/toolbox/grep/grep.c
+++ b/toolbox/grep/grep.c
@@ -403,7 +403,7 @@
 				Aflag = 0;
 			else if (Aflag > LLONG_MAX / 10) {
 				errno = ERANGE;
-				err(2, NULL);
+				err(2, "%llu", Aflag);
 			}
 			Aflag = Bflag = (Aflag * 10) + (c - '0');
 			break;
@@ -420,10 +420,10 @@
 			l = strtoull(optarg, &ep, 10);
 			if (((errno == ERANGE) && (l == ULLONG_MAX)) ||
 			    ((errno == EINVAL) && (l == 0)))
-				err(2, NULL);
+				err(2, "strtoull");
 			else if (ep[0] != '\0') {
 				errno = EINVAL;
-				err(2, NULL);
+				err(2, "empty");
 			}
 			if (c == 'A')
 				Aflag = l;
@@ -509,10 +509,10 @@
 			mcount = strtoull(optarg, &ep, 10);
 			if (((errno == ERANGE) && (mcount == ULLONG_MAX)) ||
 			    ((errno == EINVAL) && (mcount == 0)))
-				err(2, NULL);
+				err(2, "strtoull");
 			else if (ep[0] != '\0') {
 				errno = EINVAL;
-				err(2, NULL);
+				err(2, "empty");
 			}
 			break;
 		case 'n':