Cache allowed to exceed 32-bit memory limit

[DarkAlf]

Deluge client version: 1.3.15

Deluge server version: 1.3.15, 32-bit Windows

Libtorrent version: 1.0.11.0

Client OS: Xubuntu 17.10, 64-bit

Server OS: Windows Server 2012 R2, 64-bit

No plugins enabled.

(Client is set to the English language. Server daemon unknown.)

Daemon installed from latest Windows installer. It is running as a service.

Steps to reproduce:

1. Set cache size to a value greater than the per-application memory limit of the 32-bit executable.
2. Also set a gracious cache expiry limit and acquire enough torrents to fill the cache.
3. Wait for the cache to hit the memory limit.
4. Daemon will crash and all torrents will require re-checking.

Current workaround: Set cache limit below the per-application memory limit of a 32-bit executable.

Suggested fix: When the user want to set the cache size limit, check whether the daemon is 32 or 64-bit and limit the value accordingly.