message: Include mmap_win32.c on windows
diff: @@ -520,7 +520,9 @@ libbitcoin_common_a_SOURCES = \
  #only added json_spirit so that `make dist` works properly
  if TARGET_WINDOWS
  - libbitcoin_common_a_SOURCES += cpp-ethereum/libethash/io_win32.c
  + libbitcoin_common_a_SOURCES += \
  + cpp-ethereum/libethash/io_win32.c \
  + cpp-ethereum/libethash/mmap_win32.c
  else
  libbitcoin_common_a_SOURCES += cpp-ethereum/libethash/io_posix.c
  endif
  