build: Changed to an out-of-tree build.

Header files move to ./include directory, and source files move to ./src
directory. The Makefile reflects these changes.

TODO: Change to autotools for cross-platform building.

Signed-off-by: Benoit Marcot <benoit.marcot@arm.com>
clean: Delete trailing whitespaces.

Signed-off-by: Benoit Marcot <benoit.marcot@arm.com>
misc: Fix the errno.

Presumably, initial release was using an old version of the libc with a
different errno header.

Signed-off-by: Benoit Marcot <benoit.marcot@arm.com>
misc: Fix a typo (SNDSRV -> SNDSERV).

Signed-off-by: Benoit Marcot <benoit.marcot@arm.com>