29Jun07

kes  Implement new BST_DESPOOLING blocked state. Change from locking
     during despooling in SD to blocking. This means that other threads
     can work with the device structure, in particular the reservations
     system while despooling.
28Jun07
kes  Fix return in reservation message queue that missed clearing
     the jcr lock (implemented 26Jun07 below).
kes  Rename a number of dev methods to make locking function names
     a bit clearer.
kes  Document locking in lock.c. Move lock structures to new file
     lock.h.