Dubious pull request containing...

- C??FLAGS changes to distinguish between C and C++ sources, so different -std= values can be used. (Some C++ compilers don't like -std=c99, which isn't a C++ standard...)
- PLL fix (from 408MHz to 204MHz).
- Configuring USB LEDs pin mux as output.
- Set GPIO LED and GPIO EN1V8 signals to slow slew rate -- they don't need to be fast signals, so this might limit di/dt noise a bit. Doubtful it's a real issue, but...

It unnerves me that there are also commits relating to the CPLD bitstream and .vhd, and yet those changes don't show up in the "files changed"...