fixup some comments about terrains in help.cfg added earlier
tweak the help page list of traits display, for undead units

If a unit *only* has musthave traits, then we don't count them
and omit the number, just listing 'Traits: ... , ...'. This really
only changes how undead units' traits are displayed. This looks
much better without sacrificing clarity in these cases.
add a "special notes" for defense caps, with a link to explanation

This is better than what it was doing before this commit, which was
putting the link in the text in the table.
remove server compability code for 1.11.12

this causes stderr warnings.
fix a typo s/overrided/overridden/ in help for terrains
Instead of 'yes' show the defense cap value in help.

Suggested by Soliton. Also add a line of explanation in the help
that although a value is shown, if there is a cap it is always
the same as the defensive rating of the unit on that terrain and
cannot be larger.
Merge branch 'master' of git://github.com/wesnoth/wesnoth
defense cap number always has the same color as the defense rating
Add defense caps for mushroom terrain type, tweak some fluff

This commit adds negative defense modifiers, (thus establishing
a defense cap for mushroom mixed terrain types) for the following
units:

- Mountainfoot units (includes dwarves, and incidentally giant
spider and ant)
- Gryphon Rider and Gryphon Master
- Mounted type (includes loyalist cavalry)
- Khalifate mounted and armored mounted

Essentially we are adding it for most units which have very low
defense ratings on mushrooms, so that their mixed terrain defense
ratings will not improve.

The fluff description of mushroom groves is changed in the following
way:

- Mushroom groves are no longer described as "vast underground
forests of mushrooms" because this doesn't make much sense, in the
game they also appear on the surface and not underground. So the
fluff allows that they may appear on the surface as well.
- Dwarves are explained to have particularly low defense on
mushrooms, because mushrooms have an intoxicating effect on dwarves,
and the spore clouds of mature giant mushrooms render them sluggish.
This further explains why gryphon riders are slow over the mushrooms
but gryphons without a dwarf rider are not.