Mike Fleetwood authored Mar 08, 2018 and Curtis Gedak committed Mar 26, 2018

PATCHSET OVERVIEW:

As of 31 March 2017 RHEL / CentOS 5 reached the end of their support
[1][2].  Therefore remove code which supports them.  This makes RHEL /
CentOS 6 the oldest supported distribution.  So the minimum required
versions of glibmm and gtkmm can be increased dropping some autoconf
checks and conditional code supporting older versions of these
libraries.  This will undo the bulk of these these previous bug fixes:

* GParted 0.21.0
  Bug 738706 - Add support for ext4 on RHEL/CentOS 5.x

* GParted 0.16.1
  Bug 695279 - Fix GParted doesn't compile on RHEL / CentOS 5.9

[1] Red Hat Enterprise Linux Life Cycle
    https://access.redhat.com/support/policy/updates/errata#Life_Cycle_Dates

[2] Subject: CentOS Linux 5 EOL
    https://lists.centos.org/pipermail/centos-announce/2017-April/022350.html

THIS PATCH:

Remove checks for e4fsprogs commands, removing support for ext4 on
RHEL / CentOS 5.x.  This is reverting earlier commit:
    f672f688
    Check for e4fsprogs commands for ext4 support on RHEL/CentOS 5.x (#738706)

Mkfs_cmd member variable is being kept as a convenience so that it is
created once rather than on each use.  Also note that as it is a
Glib::ustring type object, it's constructor will be called which will
initialise it to the empty string so it doesn't need initialising to the
empty string in the initialiser list of the ext2() constructor itself.

Bug 794253 - Desupport RHEL / CentOS 5 and raise minimum required
             versions to glibmm 2.14.0 and gtkmm 2.16.0