Plugin manager usability improvements

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Respect filetype.common's wordchars if a filetype doesn't have its own

Go ctags parser, Scintilla lexer and Geany support improvements

Closes #238.

error was missing in secondary keywords (also sorted alphabetically now)

Add true false iota nil into primary keywords which, while not strictly
speaking keywords (they are predeclared identifiers), are nice to have
highlighted.

In addition, disable (or make less visible) syntax highlighting not related
to go.

Unfortunately varType is Geany-only so this patch cannot be ported to ctags.

The removal of the extra { read is not the most elegant thing but making
skipType() aware of the argList collection complicates things too much.

New features include:
* struct/interface detection
* struct member parsing
* function prototype parsing

Osx vte improvements

VTE prompt fixes

Note that although the last Scintilla update was a pre-release update,
the final 3.5.6 release has no changes.

Fixes broken auto-completion popup on Windows.

Update some links

The old link was an empty page.

The old link was a 404 page.

The project moved from Google to GitHub.

Use filetype.common's wordchars instead of GEANY_WORDCHARS as default
for filetypes not having their own.  This allows to change the
wordchars for all filetypes at once.

Part of issue #492.

Fix header of translation file

On OS X /etc/bashrc does some Apple-terminal-specific thing:

# Tell the terminal about the working directory at each prompt.
if [ "$TERM_PROGRAM" == "Apple_Terminal" ] && [ -z "$INSIDE_EMACS" ]; then
    update_terminal_cwd() {
        # Identify the directory using a "file:" scheme URL,
        # including the host name to disambiguate local vs.
        # remote connections. Percent-escape spaces.
        local SEARCH=' '
        local REPLACE='%20'
        local PWD_URL="file://$HOSTNAME${PWD//$SEARCH/$REPLACE}"
        printf '\e]7;%s\a' "$PWD_URL"
    }
    PROMPT_COMMAND="update_terminal_cwd; $PROMPT_COMMAND"
fi


This however doesn't work in VTE when Geany is started from the Terminal
application so we get some strange prefix for the prompt. Unset the
TERM_PROGRAM variable so it isn't set to Apple_Terminal when running
inside VTE.

Updated pt_BR translation

The initial prompt may get corrupted so it looks something like

any/src $ het-vm ~/projects/gea

instead of

techet@techet-vm ~/projects/geany/src $

This is just the initial display problem - when enter is pressed, the
second line already shows correct prompt.

It appears that VTE isn't fully initialized when starting the shell process
and when the shell start is delayed a bit (performed on idle), the prompt
looks correct.

Add a spawn module for Geany

Thanks a lot for Dimitar's hard work, commitment and endless patience!

Closes #274, #441, and https://sourceforge.net/p/geany/bugs/943/
Should also fix https://sourceforge.net/p/geany/bugs/898/

Fix typos in messages

It was already fixed in source.