Refactor tagmanager source files architecture

Split ctags and tagmanager sources, as follows:

tagmanager/ctags: the parsers, more or less upstream CTags;
tagmanager/mio: local MIO library copy;
tagmanager/src: actual tagmanager sources.
Update Waf build system
Update makefile.win32 build system
Fix incomplete copy in tm_tags_merge() that lead to crashes
Use the same pointer type for all pointers in tm_tags_merge()

This prevents GCC from complaining about implicit casts and comparisons
between different pointer types.  It also makes the code a little less
bound at dealing with TMTags.
Update of Lithuanian translation provided by Algimantas Margevičius
Adding a missing space inside German translation
Create color scheme menu item with Glade

Now there is a dialog instead of a menu for selecting the color
schemes, the item under View->Editor can be created with Glade like the
rest of the menu.
Add a separator after the Color Schemes menu item
Update NEWS to reflect current status
Fix a missing tag on global tags merge (oops)
Do not apply color scheme upon color scheme selection dialog display

Current color scheme was applied upon color scheme selection dialog
display because the GtkTreeView::cursor-changed signal is emitted when
the tree view is initially shown (since it actually gets the focus for
the first time), uselessly re-applying the current color scheme.

This is a performance issue because when many documents are open
updating the color scheme can take a few seconds.

Now we watch for the GtkTreeSelection::changed signal on the tree
view's selection, which is only emitted when the selected item actually
changes.  We also connect to that signal after filling the tree so we
don't get notified on the initial selection setup.
Update of German translation
Don't clear styles when setting lexer id unless it has changed

This fixes styles being cleared when using the Split Window plugin.
Do not change message order for sci_set_lexer()

Scintilla mentions clearing styles after setting lexer.
Warn user if current filetype might not support color schemes

If the 'default' style isn't set to a named style, then probably the
filetype styles have been overridden with manual colors and may not
work properly with color schemes.

Note: HTML-based filetypes won't show a warning because they don't
have a 'default' style (they use 'html_default' instead).

This is a simple heuristic, but is worth having to avoid some
spurious bug reports when using the color schemes dialog.
Update copyright date in about dialog
Adjust border width of the "Credits" about tab
Show shadow around license text view in the about dialog

Since the license is a huge piece of text expected to possibly scroll
horizontally, and since most themes display the background of text
views in a different color than the default widget background color,
adding a shadow makes the edges more visible and the UI neater.
Add some more items to NEWS