ZPU: Enable debug in the networking modules.
ZPU: Fix typo in a comment in xilinx_s3_icap.c
ZPU: Make helper functions in xilinx_s3_icap.c 'static inline'.
ZPU: Implementation of Xilinx Spartan 6 ICAP.

We use it to restart FPGA after flash updates and after production bitstream load.
ZPU: Rename ICAP functions for Spartan 3 and Spartan 6 to simplify build.
ZPU: Build for Spartan 6.
ZPU: Spartan 6 ICAP debug.
ZPU: UART debug facilities.