package/poco: use poco component names in kconfig variables

For clarity, use the same names used in documentation, and component
selection in configure. Valid poco component names are defined in:
https://github.com/pocoproject/poco/blob/poco-1.11.1-release/components



Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>