Fix Databar encoding of numeric blocks < 6 chars

Blocks of fewer than 6 numeric characters were (incorrectly) encoded as
numeric data, if preceded by an alphanumeric block. Now such blocks are
encoded in ALPHA mode.

If a numeric block has more than 6 characters (or >= 4 at the end of the
stream), the data is encoded as numeric block. This should be the
intention, judging from code and comments.
Always render last data char in RSS Exp Stacked mode

This was missed if the amount of data characters was even (e.g. 12 data
characters). The final data character and finder pattern would not be
included in the barcode. This makes 8+5=13 elements (whereas a full code
block has 8+5+8=21 elements). Hence the current_block_size is
introduced.

The latch at the end for the last row needed to be changed too; the
special case last row should only be triggered if the amount of symbols
on the last row is even.

This should fix most if not all unscannable GS1 Barcode Expanded Stacked
barcodes generated by Zint.
Merge remote-tracking branch 'origin/master' into databarfix
rssexp stacked: Fix segmentation fault on even number of data chars

The last data char is first in the last row (if the last row is partial) -
 hence, the limited block size of 13 is not necessarily the last block.

The bug caused uninitialized data to be copied, resulting in a segfault
when setting the actual modules.
Simplify some code for finder counts

The code is somewhat more readable now, rather than repeating the same
calculation over and over again
Correct placement of last row elements

Placement was a bit off in some cases, it should now work correctly.
Fix latch of last row (reverse black/white)

Judging from other code, resetting the latch shouldn't happen if the
amount of options per row is even.

Also, do not reset the latch anymore if the amount of data symbols
(option_2) that fits on a row is smaller than the available data.
Fix crash due to signedness in msi_plessey_mod1110
Merge remote-tracking branch 'remotes/hoffmans/databarfix'
Merge remote-tracking branch 'proxi/master'