[RAPPS] has problems with the progress bar for files that are >4GB

[RAPPS] has problems with the progress bar for files that are >4GB.
I do report that against 0.4.15-dev-3725-gadfef37.

available.h ULONG m_SizeBytes;
stores the files size as integer.
It is used later in loaddlg.cpp as a fallback mechanism, if http does not tell rapps the correct size for some reason.

available.h

member ULONG m_SizeBytes;

and
loaddlg.cpp

struct DownloadInfo member ULONG SizeInBytes;

and

ULONG dwContentLen, dwBytesWritten, dwBytesRead, dwStatus;

ULONG dwCurrentBytesRead = 0;

ULONG dwStatusLen = sizeof(dwStatus);

all such stuff should use 64bit unsigned types to properly support big files for the progressbar.