Minor documentation fix.
[autofit] Fix Savannah bug #42148.

The adaptation of the cjk auto-hinter module to blue stringsets in
2013-08-25 had three severe bugs.  Mea culpa.

1. Contrary to the latin auto-hinter, characters for reference and
   overshoot values of a blue zone are specified separately.  Due to
   the screwed-up change it didn't work at all.

2. A boolean comparison was erroneously replaced with a cast,
   causing invalid results with the `^' operator later on.  The
   visual artifact caused by this problem is the topic of the bug
   report.

3. Two flag values were inverted, causing incorrect assignment of
   reference and overshoot values.

* src/autofit/afblue.dat: Fix CJK bluestrings, introducing a new
syntax to have both reference and overshoot characters in a single
string.  This is error #1.
Add extensive comments.

* src/autofit/afblue.hin (AF_BLUE_PROPERTY_CJK_FILL): Removed, no
longer used.
(AF_BLUE_PROPERTY_CJK_TOP, AF_BLUE_PROPERTY_CJK_HORIZ): Fix values.
This is error #3.

* src/autofit/afblue.c, src/autofit/afblue.h: Regenerated.

* src/autofit/afcjk.c (af_cjk_metrics_init_blues): Correct error #1.
Use character `|' to separate characters for reference and overshoot
values.
Improve tracing messages, synchronizing them with the latin
auto-hinter.
(af_cjk_hints_compute_blue_edges): Fix value of `is_top_right_blue'.
This is error #2.
(af_cjk_align_linked_edge): Add tracing message.

* src/autofit/afcjk.h (AF_CJK_IS_FILLED_BLUE): Removed, no longer
used.
* src/sfnt/pngshim.c (error_callback): s/longjmp/ft_longjmp/.
* src/raster/ftraster.c (Vertical_Sweep_Span): Use drop-out mode.

This spot has been missed while introducing support for various
drop-out modes years ago (including no drop-out mode, which this
commit fixes).

Problem reported by Patrick Thomas <pthomas505@gmail.com>.
Minor.
* src/autofit/hbshim.c: Partially revert commit from 2014-04-17.

Using input glyph coverage data is simply wrong.

Problem reported by Nikolaus Waxweiler <madigens@gmail.com> and
Mantas Mikulėnas <grawity@gmail.com>.
[autofit] Introduce neutral blue zones to the latin module.

Such blue zones match either the top or the bottom of a contour.  We
need them for scripts where accent-like elements directly touch the
base character (for example, some vowel signs in Devanagari, cf.
U+0913 or U+0914).

* src/autofit/afblue.hin (AF_BLUE_PROPERTY_LATIN_NEUTRAL): New
property.

* src/autofit/afblue.h: Regenerated.

* src/autofit/aflatin.h (AF_LATIN_IS_NEUTRAL_BLUE): New macro.
(AF_LATIN_BLUE_NEUTRAL): New enumeration value.

* src/autofit/aflatin.c (af_latin_metrics_init_blues,
af_latin_hints_compute_blue_edges): Handle neutral blue zones.
[autofit] Fix handling of neutral blue zones in stems.

* src/autofit/afhints.h (AF_Edge_Flags): New value
`AF_EDGE_NEUTRAL'.

* src/autofit/aflatin.c (af_latin_hints_compute_blue_edges): Trace
neutral blue zones with AF_EDGE_NEUTRAL.
(af_latin_hint_edges): Skip neutral blue zones if necessary.
[autofit] Add blue-zone support for Devanagari.

This essentially moves the Devanagari script from the `Indic' hinter
to the `Latin' hinter.  Thanks to Girish Dalvi
<girish.dalvi@gmail.com> for guidance with blue zone characters!

* src/autofit/afblue.dat: Add blue zone data for Devanagari.

* src/autofit/afblue.c, src/autofit/afblue.h: Regenerated.

* src/autofit/afscript.h: Add Devanagari standard characters and
move data out of AF_CONFIG_OPTION_INDIC block.

* src/autofit/afranges.c: Move Devanagari data out of
AF_CONFIG_OPTION_INDIC block.
Move U+20B9, (new) Rupee sign, from Latin to Devanagari.

* src/autofit/afstyles.h: Update Devanagari data; in particular, use
AF_WRITING_SYSTEM_LATIN.
Formatting.
Merge branch 'master' of git://git.sv.nongnu.org/freetype/freetype2