[[ Bug 13671 ]] Keep track of delimiter length when iterating over line or item chunks
[[ Bug 13680 ]] Ensure multichar delimiters are taken into account when marking item and line chunks for wholechunk operations
[[ Bug 13674 ]] Implement MCLinuxDesktop::GetFreeDiskSpace().

The documentation for "the diskSpace" says:

> Returns the amount of free space on the disk that holds the
> defaultFolder
> ...
> Use the diskSpace function to determine whether there is enough free
> space to complete an action (such as downloading data).

There are two different ways to interpret this when implementing using
statvfs(3):

1) statvfs.f_bfree gives the number of blocks that are free.  This
   matches the stated definition of the diskSpace function.

2) statvfs.f_bavail gives the number of blocks that are available to
   use by non-superuser users.  This is much more useful for the
   stated *application* fo the diskSpace function.

This patch implements option (1).  Option (2) is commented out in the
source code.
[[ Bug 12786 ]] Treat XK_ISO_Left_Tab the same as XK_Tab.

On Xorg systems, a <Tab> keystroke has keysym XK_Tab, but a
<Shift>+<Tab> keystroke has keysym XK_ISO_Left_Tab (with the shift
modifier bit set).

Modifying the translatekeysym() function to translate XK_ISO_Left_Tab
into XK_Tab ensures that <Shift>+<Tab> key combinations are handled
correctly.
[[ Bug 12786 ]] Add bugfix note.
[[ Bug 13674 ]] Add bugfix note.
Merge pull request #1276 from runrevali/bugfix-13671

[[ Bug 13671 ]] Track delimiter length when iterating over line/item chunks
Merge pull request #1280 from runrevali/bugfix-13680

[[ Bug 13680 ]] Handle multichar delimiters when marking item/line chunks for wholechunk ops.
Merge pull request #1282 from peter-b/bugfix-13674

[[ Bug 13674 ]] Implement MCLinuxDesktop::GetFreeDiskSpace().
Merge pull request #1284 from peter-b/bugfix-12786

[[ Bug 12786 ]] Treat XK_ISO_Left_Tab the same as XK_Tab.