v5.5.1alpha
Docs: Change quoting style from `...' to '...'.
Docs: Move xz_pipe_comp.c and xz_pipe_decomp.c to doc/examples_old.
Docs: Update website URLs.
Docs: Cleanup line wrapping a bit.
Docs: Update .xz file format specification to 1.2.0.
Move doc/logo/xz-logo.png to "doc" and Doxygen footer to "doxygen".
