The third variant of changes in yosys-tests

Fix failed tests for ice40_wrapcarry; Add tests for new options.

- Fix abc_model.v to abc9_model.v in techlibs paths;
- synth_xilinx. Add tests for new options;
- synth_ecp5. Add tests for new options;
- Expand coverage for synth_dsp command;

Fix regressions on build #177 and #179; 

Xilinx UG901 test. Divide to separate tests for each case.

New tests for closed issues and open bugs. Not grepping strings where it is possible.

Divided to understand regress on #171  build.

Supporting tests for Xilinx DSP -- YosysHQ/yosys#1359

Fix regression on #160 build.