bt-linux, bt-monitor-linux: use PCAP_ERROR_ codes.

Use them rather than numerical values.

(cherry picked from commit 844f9d7ddff47c58f27b76c1620f38345ba73627)
diff --git a/pcap-bt-linux.c b/pcap-bt-linux.c
index 73548bd..e847c02 100644
--- a/pcap-bt-linux.c
+++ b/pcap-bt-linux.c
@@ -86,7 +86,7 @@
 			return 0;
 		pcapint_fmt_errmsg_for_errno(err_str, PCAP_ERRBUF_SIZE,
 		    errno, "Can't open raw Bluetooth socket");
-		return -1;
+		return PCAP_ERROR;
 	}
 
 	dev_list = malloc(HCI_MAX_DEV * sizeof(*dev_req) + sizeof(*dev_list));
@@ -94,7 +94,7 @@
 	{
 		snprintf(err_str, PCAP_ERRBUF_SIZE, "Can't allocate %zu bytes for Bluetooth device list",
 			HCI_MAX_DEV * sizeof(*dev_req) + sizeof(*dev_list));
-		ret = -1;
+		ret = PCAP_ERROR;
 		goto done;
 	}
 
@@ -112,7 +112,7 @@
 	{
 		pcapint_fmt_errmsg_for_errno(err_str, PCAP_ERRBUF_SIZE,
 		    errno, "Can't get Bluetooth device list via ioctl");
-		ret = -1;
+		ret = PCAP_ERROR;
 		goto free;
 	}
 
@@ -133,7 +133,7 @@
 		 */
 		if (pcapint_add_dev(devlistp, dev_name, PCAP_IF_WIRELESS, dev_descr, err_str)  == NULL)
 		{
-			ret = -1;
+			ret = PCAP_ERROR;
 			break;
 		}
 	}
@@ -343,7 +343,7 @@
 		if (handle->break_loop)
 		{
 			handle->break_loop = 0;
-			return -2;
+			return PCAP_ERROR_BREAK;
 		}
 		ret = recvmsg(handle->fd, &msg, 0);
 	} while ((ret == -1) && (errno == EINTR));
@@ -355,7 +355,7 @@
 		}
 		pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
 		    errno, "Can't receive packet");
-		return -1;
+		return PCAP_ERROR;
 	}
 
 	pkth.caplen = (bpf_u_int32)ret;
diff --git a/pcap-bt-monitor-linux.c b/pcap-bt-monitor-linux.c
index 9abd97b..e411587 100644
--- a/pcap-bt-monitor-linux.c
+++ b/pcap-bt-monitor-linux.c
@@ -84,7 +84,7 @@
                 PCAP_IF_WIRELESS|PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE,
                 "Bluetooth Linux Monitor", err_str) == NULL)
     {
-        ret = -1;
+        ret = PCAP_ERROR;
     }
 
     return ret;
@@ -121,7 +121,7 @@
         if (handle->break_loop)
         {
             handle->break_loop = 0;
-            return -2;
+            return PCAP_ERROR_BREAK;
         }
         ret = recvmsg(handle->fd, &msg, 0);
     } while ((ret == -1) && (errno == EINTR));
@@ -133,7 +133,7 @@
         }
         pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
             errno, "Can't receive packet");
-        return -1;
+        return PCAP_ERROR;
     }
 
     pkth.caplen = (bpf_u_int32)(ret - sizeof(hdr) + sizeof(pcap_bluetooth_linux_monitor_header));
@@ -163,7 +163,7 @@
 {
     snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
         "Packet injection is not supported yet on Bluetooth monitor devices");
-    return -1;
+    return PCAP_ERROR;
 }
 
 static int