Log Message:
Update regular php-xdebug to 2.6.0, and remove php-xdebug-devel

NOTE: xdebug 2.6.0 drops support for PHP 5.6.x

Changes since 2.5.5 (see also https://xdebug.org/updates.php#x_2_6_0):

[2018-01-29] — Xdebug 2.6.0
Fixed bugs

Fixed bug #1522: Remote debugging test failures on s390 (Big Endian).

[2018-01-23] — Xdebug 2.6.0RC2
Fixed bugs

Fixed bug #1521: xdebug_gc_stats.* missing from 2.6.0RC1 tarball.

[2018-01-22] — Xdebug 2.6.0RC1
Added features

Fixed bug #1506: Add garbage collection statistics feature (Benjamin Eberlei).
Fixed bug #1507: Add functions to access Zend Engine garbage collection metrics \ 
(Benjamin Eberlei).
Improvements

Fixed bug #1510: Change switch/case "break intentionally missing" \ 
comments to use GCC 7's new "fallthrough" attribute.
Fixed bug #1511: Detect and use compiler flags through new configure option.
Fixed bugs

Fixed bug #1335: Debugging with PhpStorm sometimes gives "can not get \ 
property".
Fixed bug #1454: Invalid memory read or segfaults from a __call() method.
Fixed bug #1508: Code coverage filter not checked in xdebug_common_assign_dim \ 
handler.
Fixed bug #1509: Code coverage missing for case inside switch with PHP 7.2.
Fixed bug #1512: Xdebug does not properly encode and escape properties with \ 
quotes and \0 characters.
Fixed bug #1514: Variable names with a NULL char are cut off at NULL char.
Fixed bug #1515: Object property names with a NULL char are cut off at NULL char.
Fixed bug #1516: Can't fetch variables or object properties which have \0 \ 
characters in them.
Fixed bug #1517: Notifications incorrectly specify the error type in \ 
"type_string" instead of "type".

[2017-12-28] — Xdebug 2.6.0beta1
Added features

Fixed bug #1059: Add filter capabilities to tracing, stack traces, and code coverage.
Fixed bug #1437: Add X-Profile-File-Name header when a profile file has been \ 
generated.
Improvements

Fixed bug #1493: Run test suite in AppVeyor for Windows CI.
Fixed bug #1498: Use new ZEND_EXTENSION API in config.w32 build scripts. (Kalle)
Fixed bugs

Fixed bug #702: Check whether variables tracing also works with =&.
Fixed bug #1501: Xdebug var dump tries casting properties.
Fixed bug #1502: SEND_REF lines are not marked as covered.

[2017-12-02] — Xdebug 2.6.0alpha1
Added features

Implemented bug #474: Added "memory" output to profiling files, to \ 
find out where memory is allocated.
Implemented bug #575: Dump super globals contents to error log upon errors, just \ 
like when this would happen for stack traces.
Implemented bug #964: Parse X-Forwarded-For for the first IP address when \ 
selecting the remote_connect_back host (Steve Easley).
Implemented bug #990: Add DBGp: notifications for notices and warnings to be \ 
shown in IDEs.
Implemented bug #1312: Implement extended_properties feature to remote debugging \ 
to support names and values with low ASCII values.
Implemented bug #1323: Added xdebug.filename_format setting to configure the \ 
formatting of filenames when tracing.
Implemented bug #1379: Added support for Unix domain sockets to \ 
xdebug.remote_host (Sara Golemon).
Implemented bug #1380: Added xdebug_is_debugger_active() that returns true when \ 
debugger is connected.
Implemented bug #1391: Added support for earlier stack frames through new \ 
argument for xdebug_call_* functions.
Implemented bug #1420: Handle PHP 7.2's new methods for switch/case
Implemented bug #1470: Added xdebug.remote_timeout to make connect timeout \ 
configurable.
Implemented bug #1495: Make var_dump() also use the new xdebug.filename_format \ 
when formatting filenames.
Improvements

Implemented bug #847: Added support for "%s" specifier for \ 
xdebug.trace_output_name.
Implemented bug #1384: Compile warning on Ubuntu 16.04 with GCC 5.4.x.
Implemented bug #1401: Improved error message in case the connection breaks.
Implemented bug #1430: Change DBGp tests to use TEST_PHP_EXECUTABLE instead of \ 
hard coded 'php'
Implemented bug #1484: Use FD_CLOEXEC with debugging sockets to prevent FDs from \ 
leaking to forked processes (Chris Wright).
Improve the foldexpr in xt.vim to fold lines correctly (Donie Leigh).
Fixed bugs

Fixed bug #1272: property_get doesn't return @attributes for SimpleXMLElement.
Fixed bug #1305: Property names with quotes can not be fetch while debugging.
Fixed bug #1431: Fix "use after free" with in \ 
add_name_attribute_or_element.
Fixed bug #1432: Fixed memory leak with xdebug_path_info_dtor.
Fixed bug #1449: Debugging breaks with array element keys containing low-ASCII \ 
variables.
Fixed bug #1471: Tracing crashes with return_assignments and ternairy operator.
Fixed bug #1474: Crashes due to variable resolving/reading mechanism not taking \ 
care of temporary hash tables correctly (Nikita Popov, Derick).
Fixed bug #1481: Fixed s390x and ppc64 builds (Remi Collet).
Fixed bug #1486: Crash on ZEND_SWITCH_LONG / ZEND_SWITCH_STRING with more than \ 
32 cases.
Fixed bug #1496: Rewrite README.rst to be more clear on how to install and build \ 
Xdebug.
Changes

Fixed bug #1411: Use Error (Throwable) instead of fatal error when maximum \ 
nesting level is reached.