TaskPointRenderer: use GeoPoint::Invalid()

Eliminate the location_available parameter.
po: update Spanish translation
po: update French translation
ArrowPagerWidget: fix typo
ArrowPagerWidget: add page flipped callback function
dlgChecklist: don't use XML layout

Use ArrowPagerWidget.
OpenGL/Init: move code to IsBlacklistedOESDrawTexture()
OpenGL/Init: blacklist OES_draw_texture only on Android

These GPUs are present only on Android devices so far; eliminate this
binary code for the runtime check on all other platforms.
Dialogs/dlgChecklist: Create dialog before calling UpdateCaption

xcsoar: ./src/Screen/Window.hpp:799: const PixelRect Window::GetClientRect() const: Assertion `IsDefined()' failed.

Program received signal SIGABRT, Aborted.
0x00007ffff5dadd95 in raise () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff5dadd95 in raise () from /lib64/libc.so.6
#1  0x00007ffff5daf2ab in abort () from /lib64/libc.so.6
#2  0x00007ffff5da68fe in __assert_fail_base () from /lib64/libc.so.6
#3  0x00007ffff5da69a2 in __assert_fail () from /lib64/libc.so.6
#4  0x000000000045c439 in Window::GetClientRect (this=0x7fffffffd300)
    at ./src/Screen/Window.hpp:799
#5  0x0000000000590e7d in WndForm::UpdateLayout (this=0x7fffffffd300) at src/Form/Form.cpp:158
#6  0x0000000000591fa0 in WndForm::SetCaption (this=0x7fffffffd300,
    _caption=0x7fffffffcf00 "Checklist: START") at src/Form/Form.cpp:638
#7  0x000000000051a19a in UpdateCaption (form=..., page=0) at src/Dialogs/dlgChecklist.cpp:60
#8  0x000000000051a55c in dlgChecklistShowModal () at src/Dialogs/dlgChecklist.cpp:153
#9  0x000000000047fc32 in InputEvents::eventChecklist (misc=0x6ebc23 "")
    at src/Input/InputEventsActions.cpp:200
#10 0x000000000047eec4 in InputEvents::processGo (eventid=27) at src/Input/InputEvents.cpp:427
#11 0x000000000047ebe9 in InputEvents::ProcessEvent (event_id=28) at src/Input/InputEvents.cpp:267
#12 0x000000000046af7f in MenuBar::Button::OnClicked (this=0xd42b50) at src/Menu/MenuBar.cpp:94
#13 0x00000000005b8b42 in ButtonWindow::OnMouseUp (this=0xd42b50, x=59, y=54)
    at src/Screen/Custom/ButtonWindow.cpp:124
#14 0x00000000005bb766 in ContainerWindow::OnMouseUp (this=0xae19d0, x=539, y=438)
    at src/Screen/Custom/ContainerWindow.cpp:175
#15 0x00000000004ded02 in MainWindow::OnMouseUp (this=0xae19d0, x=539, y=438)
    at src/MainWindow.cpp:599
#16 0x00000000005be7f1 in TopWindow::OnEvent (this=0xae19d0, event=...)
    at src/Screen/SDL/TopWindow.cpp:100
#17 0x00000000005c07ca in EventLoop::Dispatch (this=0x7fffffffd880, _event=...)
    at src/Event/SDL/Loop.cpp:64
#18 0x00000000005be884 in TopWindow::RunEventLoop (this=0xae19d0)
    at src/Screen/SDL/TopWindow.cpp:121
#19 0x00000000005500a5 in main (argc=4, argv=0x7fffffffd9f8) at src/XCSoar.cpp:143
dlgChecklist: Remember last opened checklist.

Implements TRAC #3110
Built on Fedora 19.
Require
sudo yum install -y bitstream-vera-sans-mono-fonts.noarch
OrderedTask: check location.IsValid() in GlideSolutionRemaining()

Fixes assertion failure in "Fly" mode when GPS is lost.
Merge branch 'v6.7.x'
ArrowPagerWidget: add support for an "extra" Widget

Placed in the remaining area.
VegaConfigurationDialog: don't use XML layout