Call to DllMain when unloading reflective DLL

Prior to this fix, DllMain with the ProessDetach flag was not called
when unloading the reflectively loaded DLL. This was causing very weird
crashes in the Invoke-NinjaCopy script which is built on this script.
This should fix the crash.

Author: clymb3r

CodeExecution/Invoke-ReflectivePEInjection.ps1

@@ -2620,6 +2620,15 @@ Blog on modifying mimikatz for reflective loading: http://clymb3r.wordpress.com/
 				    $ImportDescriptorPtr = Add-SignedIntAsUnsigned ($ImportDescriptorPtr) ([System.Runtime.InteropServices.Marshal]::SizeOf($Win32Types.IMAGE_IMPORT_DESCRIPTOR))
 			    }
 		    }
+			
+			#Call DllMain with process detach
+			Write-Verbose "Calling dllmain so the DLL knows it is being unloaded"
+			$DllMainPtr = Add-SignedIntAsUnsigned ($PEInfo.PEHandle) ($PEInfo.IMAGE_NT_HEADERS.OptionalHeader.AddressOfEntryPoint)
+			$DllMainDelegate = Get-DelegateType @([IntPtr], [UInt32], [IntPtr]) ([Bool])
+			$DllMain = [System.Runtime.InteropServices.Marshal]::GetDelegateForFunctionPointer($DllMainPtr, $DllMainDelegate)
+			
+			$DllMain.Invoke($PEInfo.PEHandle, 0, [IntPtr]::Zero) | Out-Null
+		
 
 		    $Success = $Win32Functions.VirtualFree.Invoke($PEHandle, [UInt64]0, $Win32Constants.MEM_RELEASE)
 		    if ($Success -eq $false)