catch some stupid input files
first iteration of a CMake file to build the shared test library

this is only a first version with remaining issues:
- currently only uses one of the files present in ./tests, as ./tests/PixTestSetVana.cc causes compiler errors.
- the shared library still depends on files from ./main.
make global daq buffer size variable in API implementation useful

- init _daq_buffersize (used only in debug output statements currently and for daqstatus()) with
DTB_SOURCE_BUFFER_SIZE (from constants.h, default buffer size in HAL); was prev. set to 0
- pass _daq_buffersize to HAL through daqstart()