gen/build: merge with migen 0575c749e35a7180f0dca408e426af8eef22b568 and reintegrate...

gen/build: merge with migen 0575c749e35a7180f0dca408e426af8eef22b568 and reintegrate migen simulator

* fhdl/visit: determinism
* structure/Case/makedefault: fix corner cases
* fhdl/tools: apply lowerer to specials in deterministic order
* fhdl/verilog: fix variable name conflict
* fhdl/verilog: simpler names for IOs. Closes #40
* fhdl/namer: deterministic naming of signals with name_override
* use https url for m-labs.hk
* pipistrello: make PMOD an extension header
* vivado: find clock nets by get_nets, not get_ports
* build: support platform-independent false path designation
* sim: add more signals to VCD (#36)
* build/xilinx: fix error message when Xilinx toolchain directory exists but does not contain a ISE version directory. Closes #39
* kc705: make xadc an extension header
* kc705: add xadc/ams gpios
* Merge branch 'master' of github.com:m-labs/migen
* conda: fix for conda-build > 1.19
* platforms/kc705: enable on-die termination for user_sma_clock
* README: update
* Revert "conda: use BUILDNUMBER from environment."
This reverts commit b2eedfd2e24f0b83c2fb118a3f98cf349b256e91.
* conda: use BUILDNUMBER from environment.
* typo
* Exception now has helpful string.
* README: remove outdated build badge
* sim: run MemoryToArray before lowering specials
* fhdl/simplify/MemoryToArray: remove spurious memory ports from specials
* sim: make unlowered specials an error
* sim: lower specials, closes #34
* sim: support evaluating Replicate()
* Revert "README.md->rst"
* Prevent backslashes in (Windows) paths from being escaped by OpenOCD's TCL implementation.
* Revert "conda: run tests as a part of package build."
* Revert "setuptools: include examples as migen.examples."
* Revert "test: also look for examples in [.../dist-packages]/migen/examples/."
* conda: use source from the current checkout.
* travis: disable (superseded by our buildbot).
* test: also look for examples in [.../dist-packages]/migen/examples/.
* setuptools: include examples as migen.examples.
* conda: run tests as a part of package build.
* build: return to current working directory after building
* sim/vcd: support signals not appearing in FHDL
* sim: deterministic clock iteration
* sim: add support for passive generators
* fhdl/structure: fix last test in _Value.__bool__ (a instead of b)