Support for UNIX sockets

Add a new config param, Server.FileSocket. When
Server.FileSocket
is set it will be used inplace of a network socket for the primary
server. This uses a new parameter to ServerOptions, m_useFileSocket,
to toggle between treating the address as a socket path or a network
address.

To initialize a socket connection thrift expects the socket file to not
exist. To support this the 'something nice' retry in startServer will
unlink an existing socket only if fuser claims it is unused.
Server.EvilShutdown enables unlinking the socket regardless of current
users.

Closes #1594

Reviewed By: @ptarjan

Differential Revision: D1135876

Pulled By: @sgolemon
Fix Zend strrpos compatibility

Fixes Zend strrpos compatibility and adds test.

Closes #1564
Closes #1632

Reviewed By: @bertmaher

Differential Revision: D1142139

Pulled By: @scannell
Define missing IMAGETYPE_ constants

Defined IMAGETYPE_UNKNOWN and IMAGETYPE_COUNT

Closes #1634
Closes #1638

Reviewed By: @ptarjan

Differential Revision: D1144855

Pulled By: @scannell
Prevent garbage on DNS_TXT records

Bug #64458 fixed an off by one error when decoding TXT records
that resulted with garbage at the end of the string returned.

Reviewed By: @scannell

Differential Revision: D1146140
Fix scoping for evaling default ReflectionParameter values

Closes #1449
Closes #1652

Reviewed By: @ptarjan

Differential Revision: D1141045
Fix spl_autoload_unregister($unused_but_valid_handler)

If a valid handler is passed in, but wasn't registered, we'd just remove the last one:

- find_if() would return ::end()
- erase() treats that to mean erase the last one

Behavior in the new test was:
- correctly remove 'b'
- incorrectly remove 'a' when asked to remove 'b' again
- segfault when asked to remove 'b' a third time

Reviewed By: @ptarjan

Differential Revision: D1145531
Fix memory management for xinclude nodes

Previously: ==580== ERROR: AddressSanitizer: attempting free on address which was not malloc()-ed: 0x604400212103

We were recursively freeing the node, including the attribute nodes - however, libxml2 doesn't malloc them separately - all we needed to do was unlink and free the root.

This fixes a fatal in PHPUnit's test suite.

Reviewed By: @ptarjan

Differential Revision: D1144722
Fix incorrect ownerDocument after DOMDocument::createElement

Closes #1551

Fixed while investigating an ASAN failure when running PHPUnit's suite.

Reviewed By: @ptarjan

Differential Revision: D1144627