Patch UnRAR: limit dict winsize to 1GB

Prevent allocating more than 1GB regardless of what is requested.
RAR dictionary sizes may not be larger than 1GB, at least in the current
version.

This is a cherry-pick of commit 9b444e7

libclamunrar/unpack.cpp

@@ -91,6 +91,12 @@ void Unpack::Init(size_t WinSize,bool Solid)
   if ((WinSize>>16)>0x10000) // Window size must not exceed 4 GB.
     return;
 
+  // Unrar does not support window size greather than 1GB at this time.
+  // Any request for a window larger than 1GB should be ignored.
+  const size_t MaxAllocSize=0x40000000;
+  if (WinSize>MaxAllocSize)
+    WinSize=MaxAllocSize;
+
   // Archiving code guarantees that window size does not grow in the same
   // solid stream. So if we are here, we are either creating a new window
   // or increasing the size of non-solid window. So we could safely reject
@@ -265,7 +271,7 @@ void Unpack::MakeDecodeTables(byte *LengthTable,DecodeTable *Dec,uint Size)
     Dec->DecodeLen[I]=(uint)LeftAligned;
 
     // Every item of this array contains the sum of all preceding items.
-    // So it contains the start position in code list for every bit length. 
+    // So it contains the start position in code list for every bit length.
     Dec->DecodePos[I]=Dec->DecodePos[I-1]+LengthCount[I-1];
   }
 
@@ -328,7 +334,7 @@ void Unpack::MakeDecodeTables(byte *LengthTable,DecodeTable *Dec,uint Size)
     uint BitField=Code<<(16-Dec->QuickBits);
 
     // Prepare the table for quick decoding of bit lengths.
-  
+
     // Find the upper limit for current bit field and adjust the bit length
     // accordingly if necessary.
     while (CurBitLength<ASIZE(Dec->DecodeLen) && BitField>=Dec->DecodeLen[CurBitLength])