test/CMakeLists.txt: Fix Boost version requirement.

The current requirement is 1.42, the 1.46 in test/CMakeLists.txt is a
copy-paste error. This was noticed since OpenBSD currently ships 1.42
and the tests would not build there.
Adjust to libsigrokdecode API changes
Use new probe_groups API
Ported Annotation to new srd_proto_data_annotation structure
Fix incorrect #include for glib.

The #include should be <glib.h>, pkg-config takes care of the include
directories etc.

This fixes the build on e.g. NetBSD.
Removed spurious declaration
Added decode error display
Moved decoder config into the popup
Renamed DecodeSignal to DecodeTrace
Factored out DecoderMenu
Adjusted annotation height
Integrated stacking button
Renamed pv::data::Decoder to DecoderStack
Implemented decoder stacking
Reduced popup padding
Added .gitignore rules for ninja-build files, and Vim swp files
Slightly offset the PopupToolButton popup
Added missing includes to popuptoolbutton.{h,cpp}
Added Popup::closed signal
Added missing forward-declaration to DecodeTrace