cp uim-vi-1.8 commit #774dcbf :Add empty files to support uim-vi-xtelex

See also TheSLinux/buildystem/uim-vi @ 2790ca8
cp uim-vi-1.8 commit #34556cf Clean up some non-vi modules/language supports

Conflict resolved:
+ po/LINGUAS: remain LINGUAS content on master branch, see #d363a36 for
more details.
+ scm/Makefile.am: clean up some non-vi modules/language we don't use
any more. Remain changes on uim-vi-1.8 for this file.
cp uim-vi-1.8 commit #a9a3938 Add new module :xtelex

This module is a big table of predefined words for Telex users.
Pls check details at https://github.com/icy/myquartz-scim2uim
cp uim-vi-1.8 commit #635facd: Add new module :xvni

This module is a big table of predefined words for VNI users.
It is genereated from https://github.com/icy/myquartz-scim2uim/ \
  blob/master/src/VNI.txt.in
cp uim-vi-1.8 #ccd8950 Should use .png instead of .svg for vni
cp uim-vi-1.8 commit #7500f77: + IPA support xtelex-ipa, xvni-ipa
cp uim-vi-1.8 commit #d3e7492 + config. to set default mode for generic IM

New configuration option allows user to select default mode
for generic IM. This is useful but it may be buggy if some IM
has its own configuration to do the samething.

FIXME: Add test cases
cp uim-vi-1.8 commit #a783a84 Hide/show candidate window via generic option

Conflict resolved:
+ scm/m17nlib.scm: Remain changes on uim-vi-1.8 for generic option
instead of m17nlib option.
cp uim-vi-1.8 commit #e5e11f5 m17nlib now requires :generic-custom

This is bc we want to use :generic-use-candidate-window?
-- that variable is defined in "generic-custom".

A dicussion on this topic can be found on Github
  https://github.com/uim/uim/pull/25
cp uim-vi-1.8 commit #08f9801 Remove some Japanese supports from :toolbar.menu

They are:
* Japanese dictionary editor
* Handwriting input pad

The configuration directives disable support for them, so they
actually do not work when user select them from the menu.

We use :UIM_VI_NO_CLEAN_UP to disable the items. To turn them
on, you need to define that macro at the configuration time
cp uim-vi-1.8 commit #1701a12 Remove :state icon on systray