Add tests for commits:
- Add "wreduce -keepdc";
- Add "fmcombine -initeq -anyeq";
- Add "stat -tech xilinx";
- Add "synth_xilinx -arch".

Testing problems:

1.scc_feedback - Feedback is detected not in each case(with different
options).
2.splice/splice_port - No any changes in the dump after splice -port
command.
3.test_cell/test_cell_macc - ERROR: Assert `port_declared == true'
failed in kernel/rtlil.cc:1352.

Fix failed tests

Fix failed tests for dffe cell

Add missing files to frontends and misc; Add new tests to regression.