Add construtor with backing allocator to be able to allocate chuncks of linear memory from the main memory

engine/core/mem/LinearAllocator.cpp

@@ -30,10 +30,15 @@ namespace crown
 {
 
 //-----------------------------------------------------------------------------
-LinearAllocator::LinearAllocator(void* start, size_t size) :
-	m_physical_start(start),
-	m_total_size(size),
-	m_offset(0)
+LinearAllocator::LinearAllocator(Allocator& backing, size_t size)
+	: m_physical_start(NULL), m_total_size(size), m_offset(0)
+{
+	m_physical_start = backing.allocate(size);
+}
+
+//-----------------------------------------------------------------------------
+LinearAllocator::LinearAllocator(void* start, size_t size)
+	: m_physical_start(start), m_total_size(size), m_offset(0)
 {
 }
 

engine/core/mem/LinearAllocator.h

@@ -37,6 +37,7 @@ class LinearAllocator : public Allocator
 {
 public:
 
+				LinearAllocator(Allocator& backing, size_t size);
 				LinearAllocator(void* start, size_t size);
 				~LinearAllocator();