Makefile: Allow building without optimization - CFLAGS are always last

This would allow to build openchange w/o compiler optimizations like:
CFLAGS='-g -O0' ./configure --prefix=/usr ...
mapistore/python: Implement PT_I8 value conversion from Pyton-to-C

So we could get PidTagFolderId values
Makefile: clean mapistore_test artifacts
mapistore/oxio: Protect Table.get_row() when there is no data to get

And comment out some debug messages not to be so chatty