[LEN] to [static LEN] on some function parameters Also add STATIC_ARRAY macro to hide it in c++ compilation.

mbox: Added mbox_md5 setting to select headers for MD5 generation.

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Reorganized mbox md5 summing code so it doesn't require sync context anymore. --HG-- branch : HEAD