external tools: Use a GIOchannel also for stdin

Write into the stding pipe asynchronously using a GIOChannel in
nonblocking mode
external tools: switch to the right bottom pane page

A typo was preventing it to work
externaltools: whitespace pep8 fixes
filebrowser: plug string leak
menustackswitcher: implement finalize to free hash table
filebrowser: do not leak treepath
Unref all the menu models at shutdown
Do not leak closed tabs list
Make sure text passed to insert_text is null terminated

https://bugzilla.gnome.org/show_bug.cgi?id=726390
replace-dialog: fix corner-case button sensitivity

If the regular expression checkbutton is checked, the search entry
contains an invalid regular expression, and the user presses Find or
Replace All, all response buttons correctly become insensitive. Now, if
the user unchecks the regex checkbutton, the error should be cleared and
the responses should become sensitive so that he can search again. This
wasn't happening.

https://bugzilla.gnome.org/show_bug.cgi?id=726593
Drop libgedit-private.so

Having a noinst libgedit and an installed libgedit-private.so does
not really make much sense. Let's just install libgedit.so, it is in
a pkg specific dir anyway with no stability guarantee and (at least
on windows) C plugins need to actually link to it
W32: Include rc file by its absolute name

Otherwise you get something like this at compile time:
windres -i gedit/gedit.rc --input-format=rc -o gedit/gedit-res.o -O coff
i686-w64-mingw32-gcc: error: gedit/gedit.rc: No such file or directory
i686-w64-mingw32-gcc: warning: '-x c' after last input file has no effect
i686-w64-mingw32-gcc: fatal error: no input files

https://bugzilla.gnome.org/show_bug.cgi?id=727658
W32: don't redefine _WIN32_WINNT

https://bugzilla.gnome.org/show_bug.cgi?id=727659
Fix GI makefile rules to account for non-empty EXEEXT

https://bugzilla.gnome.org/show_bug.cgi?id=727660
W32: Remove custom libgedit.a import library

Since we have a real, shared libgedit.dll, we can have a real libgedit.dll.a
import library.

https://bugzilla.gnome.org/show_bug.cgi?id=727663
Plugins need code from shared libgedit, so link them to it

https://bugzilla.gnome.org/show_bug.cgi?id=727663
W32: Override libtool internal variables to produce a delay-load import library

We remove --out-implib, add --output-def (where needed), and add extra call
to dlltool to generate delay-load import library (name's the same as normal
import library, so tools/applications won't notice the change).
When application is linked to libgedit via such import library, the DLL is
only loaded when first function from it is called. This gives us time to
influence W32 runtime linker.

https://bugzilla.gnome.org/show_bug.cgi?id=727663
W32: load libgedit.dll at runtime

Since libgedit is linked as delay-loaded DLL, it's still not loaded when
main() is called. Before we call functions from it, we must locate
libgedit.dll and load it (otherwise, if it's not in PATH (which is how it
should be!), calling its functions will crash the program).
As comments indicate, the use of g_module_open() is not really necessary,
but, given the circumstances, it is convenient and clean.

https://bugzilla.gnome.org/show_bug.cgi?id=727663
W32: Fix .pc file LDFLAGS (assuming libgedit is in <prefix>/lib/gedit)

https://bugzilla.gnome.org/show_bug.cgi?id=727663
W32: Move installed libgedit.dll into appropriate dir

https://bugzilla.gnome.org/show_bug.cgi?id=727663