Update Common.cmake for production development.

Semantic-wise, do not default to normal_devel_tree.
Update CMakeLists.txt for production development.

Do not use any devel tree configuration if included from another CMake
project.
Android-specific: do not use pthread (it is in libc).
Android-specific: add ARM architectures.
Android-specific: add stubs for pthread thread cancellation.
Split fx_vasprintf() to fx_vasprintf() and fx_strdup(): not all implementations allow integer NULL in args.