Improved the Thumb assembler back end. Added many more Thumb
instructions to the inline assembler. Improved parsing of assembler
instructions and arguments. Assembler functions can now be passed the
address of any object that supports the buffer protocol (to get the
address of the buffer). Added an example of how to sum numbers from
an array in assembler.
It's no longer intended to provide just "raw" socket interface, may include
some convenience methods for compatibility with CPython socket - but anyway
just minimal set required to deal with socket client and servers, not wider
network functionality.
