Nine Linux-related cherry-picks from develop to release/8.0

Improve libhunspell handling on Linux

Mapping libhunspell to the actual library in the config file has
the advantage that it can be changed without recompiling the code.
The <dllmap> entry in the config file will be ignored on .NET (see
http://www.mono-project.com/Interop_with_Native_Libraries).

The original motivation for this change was that we get test
failures on Lucid where we have libhunspell-1.2. Unfortunately it
is not possible to override dllmap entries. On an end user's machine
we'd have to modify the config file (probably when building the
package). On the Lucid build agents we use a hack and create a
symlink to libhunspell-1.3 :-)

(cherry picked from commit d999a706b9c0b03f29819f1e5d3b5df20e28b777 on
develop)
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Avoid crashes when HKLM keys don't exist

It looks like this one was missed when we made the switch from
HKLM to HKCU

(cherry picked from commit 9c73d0822c836a59c72ec4e674134da378a8a18e on
develop)
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Remove DistFiles/lib from Linux install

The last files were removed from this directory in 5c0cea8 when
switching from Enchant to Hunspell

(cherry picked from commit b0e555b3d817346bc003b474c046dca522b34b10 on
develop)
================
Fix possible crash when setting linked files folder

This fixes FWNX-1062 "Flex can crash when adding an audio writing system".

(cherry picked from commit 57426fe3de73da25704ea741ddcad16c729e18cc on
develop)
================
Remove obsolete files from DistFiles/Linux

This fixes FWNX-1064.  These files are all in the fieldworks-gtk-sharp2
package, or found under /usr/local/lib/mono on developer machines once
the gtk-sharp repo has been built and installed.

(cherry picked from commit 30e1ef2533d55aaaa764a49fff94250ab2ffe0bb on
develop)
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Fix package build error on Linux

Commit 30e1ef2 removed the last of the .dll.config files from
DistFiles/Linux. As a result, the commands run by make install when
building packages encounter an error when *.dll.config doesn't match any
files.

 * Refactor the install lines to match *.dll* instead.
 * Also rearrange commands into a more logical order.

(cherry picked from commit 909da63a8d3f3ab2d89f85e3b7ed85077b524a3f on
develop)
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Adjust Linux registry settings for 8.x

This fixes FWNX-1065 and maybe a few others as well

(cherry picked from commit 517a5abd2197cbb3e8b74340040e2f2610a6c87d on
develop)
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Fix Help for multiple htm references

The paths to the htm references in the Flex HelpTopicsPaths.resx file
need leading '/' and some have trailing spaces. This will filter for
these problems in the htm references.

(cherry picked from commit e139d69dbce22490b5a925230535e72a38c588b9 on
develop)
================
Fix mistake in 909da63 "Fix package build error on Linux"

The patterns *.dll* and *.mdb both match .dll.mdb, which led to
complaints from the install utility about overwriting files.

(cherry picked from commit 9d84677205ec7b51ec9de3c538ceb1d6d0feec6f on
develop)

Change-Id: Id0f1a69435bc755364518e0cda7c4fedc5c1796f