Return nil, not false, from firewall-bypass.nse
Handle ICMP Time Exceeded messages in scan engine

DiabloHorn on #nmap noticed that Nmap was ignoring ICMP Time Exceeded
messages while trying to map firewall rules using --ttl.
get_pcap_result() was handling ICMP type 3 (Destination Unreachable),
but not type 11 (Time Exceeded). Now ports that elicit this response
will be marked filtered (to be consistent with existing Connect scan
behavior) and will report time-exceeded from (IP) for the reason.

This was not a common issue, since host discovery already accounted for
it. Port scans would only be affected when skipping host discovery.
Changelog entry for time-exceeded port reason
Update script.db
Merge r27122 from nmap-npingchanges: Changed names for output funtions. outPrint() -> nping_print(); outFatal() -> nping_fatal() ; outError() -> nping_warning(). This change is completely irrelevant but I personally hate the names I chose the first time and I thought I'd change them to something better.
Merge r27120,27121,27123,27124,27125 from nmap-npingchanges. Minor style and typo fixes.
Merged r27162 from nmap-npingchanges: Remove some unused code
Merge r27177-180 from nmap-npingchanges: Minor typo and style fixes in -h output
Merged r27296 from nmap-npingchages: Add some missing code to support ICMP domain name requests
Merged r27297 from nmap-npingchages: Implement the print() method for IPv6 headers
Merged r27539 from nmap-npingchages: Implement print() in ICMPv6Header
Merged r27540 from nmap-npingchages: Fix bug: convert to u32 after fixing the endianness.
Merged r27646 from nmap-npingchages: Add function to determine the tranport layer protocol in a chain of PacketElements
Merge r27953 from nmap-npingchanges: Add support for ARP Request/Reply packet matching
Merge r27995 from nmap-npingchanges: Add two missing codes. Also, re-write description so it says the same thing as Wireshark.
Merge r27956 from nmap-npingchanges: Improve code description.
Merge r27958 from nmap-npingchanges: Simplify print() in RawData::
Merge r27963 from nmap-npingchanges: Remove some unimplemented command-line flags
Merge r28016 from nmap-npingchanges: Add method to set IP options from a binary buffer than can be inserted right away into the IP header.
Merge r28024 from nmap-npingchanges: Make the test script executable