ZXPather

Updated pather.bas to build up the hex string in b$ instead of a$, and to isolate the newly-added segment from b$ into a$ to draw instead of redrawing the entire string every time a segment is added.

Updated faster.z80 to use ADD A,A instead of SLA A.

Trying third strategy for video embed

Trying alternate syntax for video embed in README.md.

Updated faster.z80 to use a label instead of literal address to load arguments. Updated the assembler output faster.lst. (The actual bytes are unchanged.)