Identified some addresses and structure fields, decompiled most of sub_6C0C3F.

- Added new address definitions: 
RCT2_ADDRESS_STAFF_MODE_ARRAY
RCT2_STAFF_MODE_NONE
RCT2_STAFF_MODE_NORMAL
RCT2_STAFF_MODE_PATROL

- Identified struct fields:
rct_peep->staff_id

- Decompiled subroutines: sub_6C0C3F
Only addresses to rct2 go in addresses.h. Consider using an enum in the relevant module, e.g. staff like @duncanspumpkin mentioned.