MTL set priority=0 for targets with IN_BRIGHT_OBJECT set

[sbailey]

Related to #102 (define the bright object bits) and #103 (bright object mask for mocks):

Update the MTL code to set priority=0 for any object with IN_BRIGHT_OBJECT set. This is a special case, since normally the bit with the highest priority always wins. This is completely independent of the mocks themselves — the same MTL code applies to both mocks and real targets.

[sbailey]

implemented in PR #109 but I didn't get my git comment syntax write to have it automatically close this. Closing now.