Modified the revision selection while comparing po-files$

If revision-parameter is set to e.g. '-3', now we search for the previous
3-rd change of the relevant po-file instead of the previous 3-rd commit.

We now also pass options through the environment, though it is not needed for git.
This way we overcome the deficiency of "hg" and "svn", which do not allow
to pass self-defined options to underlying diff-command.
* cs.po
Corrected displayed file-name for fuzzy and untranslated messages in diff_po.pl
sk.po, make some messages clearer
add Option-Tab resp. Option-Shift-Tab for buffer-next/previous because Control-Tab doesn't work anymore
Move AGU_article.lyx to the attic

Exporting this outdated document currently hangs on some systems.
Further, there is no natural link between AGU and DocBook
and this could be confusing to a user who is looking for
the AGU template.
Handle is_child runparam in preview (bug #8445)
cosmetics: remove unneeded std:: prefix

Amended-by: Vincent van Ravesteijn <vfr@lyx.org>
Remove dependency on TEX2LYX #define in Lexer.cpp
Remove dependency on TEX2LYX #define in ModuleList.cpp
Move tex2lyx dummy implementations in their own file.

Also try to document their use.
Remove dependency on NO_LAYOUT_CSS #define in Layout.cpp

Remove all traces of this #define.
Encodings: Add CharInfo to Encoding.h
Encodings: Split off the functions that need Buffer

This is needed to be able to use Encodings in tex2lyx without the need to
compile Buffer as well, or to use a TEX2LYX define.
Encodings: Make members of CharInfo private
Encodings: Use BufferEncodings where needed
Remove the TEX2LYX define when compiling tex2lyx
Enable automake subdir-objects
Merge: Remove tex2lyx defines to allow for newer automake

Automake version 1.14 warns that subdir-objects needs to be
enabled to avoid future incompatibilities. However, this causes problems
for objects that are compiled twice (for LyX and tex2lyx) with different
defines (e.g., TEX2LYX and NO_LAYOUT_CSS). Therefore, we need to properly
fix the code without using these defines.

See also:
 - commit 16cdf70d (Jul 26, 2013),
 - commit 3698fde0 (Aug 19, 2013), and
 - http://marc.info/?l=lyx-devel&m=137673178123427&w=2.
Replace autogenerated icons for the math toolbar

The autogenerated icons are in most cases ugly, do not conform to the
style of the other icons, and do not respect relative dimensions and
positions. The math icons have a vertical dimension of 19 pixel, defining
a grid that has to be respected for obtaining correct alignment.
The only autogenerated icons that remain are those of the Misc (extra)
toolbar. I plan to also replace them in the near future.