Form.cc: fix radiobutton reporting wrong state

When a radiobutton (belonging to a normal radiobutton group)
has a /V key matching his 'OnStr' state, then when you
ask that radiobutton for his state (eg. radiobutton->state())
it will wrongly return 'true', when really the active
radiobutton is another one in the group.

This happens because the faulty radiobutton was not passing
the getState() call to his Parent (which every radiobutton
in a group should do, as the Parent stores the value of the current
active item).

The code was not doing it because it had a valid AppearanceState
(/V key). That behaviour may be right for checkboxes but not for
radiobuttons.

A testcase is included. An example definition of an
affected radiobutton follows:

/F 4
/FT /Btn
/Ff 49152
/AP /N /Beer 59 0 R /Off 61 0 R
/AS /Beer
/MK /BC [1,0,0] /BG [1,1,1] /CA (4)
/P 20 0 R
/Parent 8 0 R
/Rect [235.277,654.247,249.224,668.194]
/Subtype /Widget
/Type /Annot
/V /Beer

Fixes issue #159
6 jobs from BUG_tcpdf_checkbox in 24 minutes and 6 seconds (queued for 28 minutes and 57 seconds)
Status Job ID Name Coverage
  Build
failed #58001
build

00:04:51

passed #58006
build_android

00:01:15

failed #58002
build_clang_libcpp

00:04:58

failed #58005
build_clazy

00:04:53

passed #58003
build_gcc_49

00:08:09

passed #58004
build_mingw64_fedora

00:03:25

 
Name Stage Failure
failed
build_clazy Build
[194/208] Building CXX object qt5/demos/CMakeFiles/poppler_qt5viewer.dir/navigationtoolbar.cpp.o
[195/208] Building CXX object qt5/demos/CMakeFiles/poppler_qt5viewer.dir/thumbnails.cpp.o
[196/208] Building CXX object qt5/demos/CMakeFiles/poppler_qt5viewer.dir/optcontent.cpp.o
[197/208] Building CXX object qt5/demos/CMakeFiles/poppler_qt5viewer.dir/toc.cpp.o
[198/208] Building CXX object qt5/tests/CMakeFiles/check_qt5_utf_conversion.dir/check_utf_conversion.cpp.o
[199/208] Building CXX object qt5/demos/CMakeFiles/poppler_qt5viewer.dir/viewer.cpp.o
[200/208] Building CXX object qt5/tests/CMakeFiles/check_qt5_pagelabelinfo.dir/check_pagelabelinfo.cpp.o
ninja: build stopped: subcommand failed.
ERROR: Job failed: exit code 1
failed
build_clang_libcpp Build

95% tests passed, 1 tests failed out of 20

Total Test time (real) = 1.47 sec

The following tests FAILED:
8 - check_qt5_forms (Failed)
Errors while running CTest
ERROR: Job failed: exit code 1
failed
build Build

95% tests passed, 1 tests failed out of 20

Total Test time (real) = 1.40 sec

The following tests FAILED:
8 - check_qt5_forms (Failed)
Errors while running CTest
ERROR: Job failed: exit code 1