Fixes #2724 and #1570.
Adds the
automatically-subtract-the-fee-from-the-amount-and-send-whats-left
feature to the GUI and RPC (sendtoaddress,sendmany).
Use misc methods of avoiding unnecesary header includes.
Replace int typedefs with int##_t from stdint.h.
Replace PRI64[xdu] with PRI[xdu]64 from inttypes.h.
Normalize QT_VERSION ifs where possible.
Resolve some indirect dependencies as direct ones.
Remove extern declarations from .cpp files.
