fixup programmer error in pager

reported by gfgtdf

this fixes up commit 75f5076d6c78ed38c1ca1c3107b71e2b20068671
remove unused variable

the variable was only used for a log message and it's not worth the
additional code complexity
removed dead code

this code had no effect except making the code look more complicated.
remove unused variable
fixup a problem in unit filter handling of strange children

Right now, many places in the code construct unit filters with
children that it ignores, for instance [message] results in
unit_filters which may have [option] children. There's no easy
way to filter those out right now, so messages of spurious
children are relegated to "debug config" channel rather than
a more prominent place (since there are likely to be many
false reports of a problem in the current arrangement.)
Merge branch 'master' of git://github.com/wesnoth/wesnoth
add an error message when parsing nested #defines in WML

This doesn't work, so it's better to give an actual message
rather than silently fail.

This is tangentially relevant to feature request #21343, I added
a code comment at the appropriate place where we might fill that
request.
fix assertion failure in unit_display.cpp, bug #22305

It was a simple programmer error I made in commit:
750e770c62d3498bbc78f3eda60c5f41d6a03b39
update changelog
replace segfault with assert.
fixup whitespace issues
move extract_summary_from_config fcn to private namespace

Since it is only used there anyways
fixup how extract_summary_from_config stores map_data

This forward ports part of e7eb08d0cd2d57b55bf084b669fbeec8d283db33
which was fixing bug 22086 in 1.12 branch.
carry forward some debugging info from 1.12 bugfix 22086

from 1.12 branch, commit e7eb08d0cd2d57b55bf084b669fbeec8d283db33
add some debugging for game_classification when loading

Carry forward some debugging info. This code was introduced
in 1.12 branch in bug fix for 22086, commit

e7eb08d0cd2d57b55bf084b669fbeec8d283db33
update changelog
remove some dead code "fill_mplevel_config"
Updated changelog
fixup [filter_vision] tags

This is the master version of PR #237, with unit tests.
add [has_ally],[has_enemy] tags for standard side filter

Unlike [allied_with] and [enemy_of], these will match if only if
there is *any* ally or enemy matching the filter. The other versions
of the tag match only if all sides matching the filter are
allied / opposed.

This commit also adds a unit test that checks that it works as
expected.