libbase: use __builtin_setjmp and __builtin_longjmp
software: remove setjmp
targets: add simple design (vendor agnostic and usable on all platforms with UART pins).

Designing a SoC with Migen is easy, but we have to provide a very simple design that can
be used on all boards with only 1 clock and 2 UARTs pins defined. This will encourage the
newcomer to invest time in Migen/MiSoC and see its real potential.
update README with new Kintex-7 support
uart: split it and use dataflow

This make the code easier to understand and allow the reuse of UARTRX & UARTTX
on designs without CPU (e.g miscope).
uart: minor cleanup and fix
mor1kx: sync
Merge branch 'master' of https://github.com/m-labs/misoc