Added libs/minisat (copy of minisat git master)
Fixed dependencies of "make test"
 - Makefile: resolve merge conflict.
 - Makefile: export PATH=${DESTDIR}/bin:$(PATH) and (DY)LD_LIBRARY_PATH, to make sure our local copies of built executables and libraries are used.
 - Makefile: use find expression in target 'yosys-svgviewer' to find svgviewer binary (qmake will build into .app package on OSX).
 - Makefile: make 'test' target dependent on $(TARGETS) and $(EXTRA_TARGETS) to make sure that minisat is built.
 - Makefile: fix typo in LDFLAGS: obviously -L, not -I is required here
 - Makefile: include $(PWD) in PATH, since 'make test' can happen before 'make install'.
Merge branch 'master' of https://github.com/Siesh1oo/yosys
 - libs/minisat/System.cc: fix definition/declaration mismatch for Minisat::memUsedPeak() and mark unused parameters as unused to fix compiler error+warning. (minisat bug tracker issues #1, #9, #10.)
 - libs/minisat/Solver.cc: insert spaces between string and PRIu64 literal, otherwise c++11-compliant compilers will bail out due to user-defined literals (minisat bug tracker #13).
 - Makefile: follow changes in https://github.com/cliffordwolf/yosys
 - .gitignore: ignore qmake/OSX package libs/svgviewer/svgviewer.app