* Unify uart drivers of different hardware drivers
* Remove deprecated IRQ activations
* Remove additional timer thread in Fiasco* KDB driver
* Move more generic UART definitions to specific supported
platforms (e.g.: pl011 -> pbxa9)
* Move internal definitions from global to local headers
Ref #1987Fix#2071
Instead of holding SPEC-variable dependent files and directories inline
within the repository structure, move them into 'spec' subdirectories
at the corresponding levels, e.g.:
repos/base/include/spec
repos/base/mk/spec
repos/base/lib/mk/spec
repos/base/src/core/spec
...
Moreover, this commit removes the 'platform' directories. That term was
used in an overloaded sense. All SPEC-relative 'platform' directories are
now named 'spec'. Other files, like for instance those related to the
kernel/architecture specific startup library, where moved from 'platform'
directories to explicit, more meaningful places like e.g.: 'src/lib/startup'.
Fix#1673
