Update php-xdebug to 2.7.0.

From Michael Moll via github.
Closes NetBSD/pkgsrc#43.

  [2019-03-06] ? Xdebug 2.7.0

      Fixed Bugs

      Fixed bug #1520: Xdebug does not handle variables and properties with
      "-" in their name
      Fixed bug #1577: Code coverage path analysis with chained catch fails
      in PHP 7.3
      Fixed bug #1639: Compile warning/error on GCC 8 or Clang due to "break
      intentionally missing"
      Fixed bug #1642: Debugger gives: "Warning: Header may not contain NUL
      bytes"
  [2019-02-15] ? Xdebug 2.7.0RC2

      Fixed Bugs

      Fixed bug #1551: Property with value null is not represented well
      Fixed bug #1621: Xdebug fails to compile cleanly on 32-bit platforms
      Fixed bug #1625: Work around ABI conflicts in PHP 7.3.0/PHP 7.3.1
      Fixed bug #1628: The PHP function name being constructed to record when
      GC Collection runs, is not freed
      Fixed bug #1629: SOAP Client/Server detection code does not handle
      inherited classes
  [2019-02-01] ? Xdebug 2.7.0rc1

      Fixed Bugs

      Fixed bug #1571: File/line information is not shown for closures in
      namespaces.
      Fixed bug #1578: Compile error due to redefinition of "zif_handler"
      with old GCCs.
      Fixed bug #1583: Xdebug crashes when OPcache's compact literals
      optimisation is on.
      Fixed bug #1598: Make path/branch coverage work with OPcache loaded for
      PHP 7.3 and later.
      Fixed bug #1620: Division by zero when GC Stats Collection runs with
      memory manager disabled.
  [2018-09-20] ? Xdebug 2.7.0beta1

      Improvements

      Fixed bug #1519: PHP 7.3 support (with a contribution by Christoph M.
      Becker)

(bsiegert)