Don't free GC allocated memory in HTTP server.

In normal allocation mode (no VibeManualMemoryManagement), the GC allocated request memory was freed anyway, potentially resulting in dangling pointers if strings read from the request were stored outside of the request handler. This switches back to the proper behavior as in 0.7.x.

http/vibe/http/server.d

@@ -1774,9 +1774,9 @@ private void handleHTTPConnection(TCPConnection connection, HTTPListenInfo liste
 			import vibe.internal.utilallocator: RegionListAllocator;
 
 			version (VibeManualMemoryManagement)
-				scope request_allocator = new RegionListAllocator!(shared(Mallocator))(1024, Mallocator.instance);
+				scope request_allocator = new RegionListAllocator!(shared(Mallocator), false)(1024, Mallocator.instance);
 			else
-				scope request_allocator = new RegionListAllocator!(shared(GCAllocator))(1024, GCAllocator.instance);
+				scope request_allocator = new RegionListAllocator!(shared(GCAllocator), true)(1024, GCAllocator.instance);
 
 			handleRequest(http_stream, connection, listen_info, settings, keep_alive, request_allocator);
 		} ();

utils/vibe/internal/utilallocator.d

@@ -5,7 +5,7 @@ public import std.experimental.allocator.mallocator;
 public import std.experimental.allocator.building_blocks.affix_allocator;
 
 
-final class RegionListAllocator(Allocator) : IAllocator {
+final class RegionListAllocator(Allocator, bool leak = false) : IAllocator {
 	import vibe.internal.memory_legacy : AllocSize, alignedSize;
 	import std.algorithm.comparison : min, max;
 	import std.conv : emplace;
@@ -154,8 +154,10 @@ final class RegionListAllocator(Allocator) : IAllocator {
 		Pool* pnext;
 		for (auto p = cast(Pool*)m_freePools; p; p = pnext) {
 			pnext = p.next;
-			m_baseAllocator.deallocate(p.data);
-			m_baseAllocator.deallocate((cast(void*)p)[0 .. AllocSize!Pool]);
+			static if (!leak) {
+				m_baseAllocator.deallocate(p.data);
+				m_baseAllocator.deallocate((cast(void*)p)[0 .. AllocSize!Pool]);
+			}
 		}
 		m_freePools = null;