uart: Initial commit
examples/serial: Initial commit
uart: Major rework
spi: Fix check for head
adc_queue: Fix queue head check
sg: Fix spelling of length
sg: Add comments
uart: Add read until operation
uart: Fix clockrate
uart: Simple handling framing error
uart: Disable RX queue

This seems to kill the peripheral for unknown reasons. Disable for now.
uart: Manage TE/RE flags automatically
uart: Ensure remaining gets reset after read_until
examples/serial: Bidirectional test
Merge pull request #109 from bgamari/uart

[RFC] UART support
toolchain: Compute available RAM after static allocations