Add GetLargeRange() function.

include/memory_space.h

@@ -51,6 +51,7 @@ class MemorySpace_t : public std::map<RangeAddress_t,char>
 			GetNearbyFreeRanges(const RangeAddress_t hint, size_t count = 0) = 0;
 		virtual void AddFreeRange(Range_t newRange)=0;
 		virtual void RemoveFreeRange(Range_t newRange)=0;
+		virtual Range_t GetLargeRange(void)=0;
 
 		// queries about free areas.
 		virtual bool AreBytesFree(RangeAddress_t addr, int num_bytes)=0;