dplayx: Fix incorrect check in DirectPlayLobbyAImpl_EnumLocalApplications and IDirectPlayLobbyAImpl_EnumAddressTypes.

Dereferencing a function pointer and checking it against NULL doesn't 
make any sense, so remove the checks.

Dereferencing a function pointer and checking it against NULL doesn't 
make any sense, so remove the check.

Some files use wine/exception.h without also including excpt.h, but 
excpt.h is needed when using native exception handling.

Instead only clear the number of bytes requested and mark the remainder 
as uninitialised.

ntdll: Fix the use of oldSize in RtlReAllocateHeap as both the size of the old block and the number of bytes used in the old block.