OFStateManager: remove error handling from callers of aim_malloc

aim_malloc will never return NULL.

Also replaced malloc+memset with aim_zmalloc.
OFConnectionManager: inline extract_read_buffer

It's a single call to memdup. The function's docs were also wrong in claiming
that it resets the read offset.
SocketManager: remove malloc error handling
Configuration: replace plain malloc with aim_malloc
Merge into master from pull request #86:
Standardize memory allocations (https://github.com/floodlight/indigo/pull/86)