atl: Implement AtlComQIPtrAssign.

dlls/atl/atl.spec

diff --git a/dlls/atl/atl.spec b/dlls/atl/atl.spec
index 6204c5d..cbeecb6 100644
--- a/dlls/atl/atl.spec
+++ b/dlls/atl/atl.spec
@@ -23,7 +23,7 @@
 28 stdcall AtlPixelToHiMetric(ptr ptr)
 29 stub AtlDevModeW2A
 30 stdcall AtlComPtrAssign(ptr ptr)
-31 stub AtlComQIPtrAssign
+31 stdcall AtlComQIPtrAssign(ptr ptr ptr)
 32 stdcall AtlInternalQueryInterface(ptr ptr ptr ptr)
 34 stub AtlGetVersion
 35 stub AtlAxDialogBoxW

dlls/atl/atl_main.c

diff --git a/dlls/atl/atl_main.c b/dlls/atl/atl_main.c
index 3b5703e..d4d950a 100644
--- a/dlls/atl/atl_main.c
+++ b/dlls/atl/atl_main.c
@@ -208,6 +208,18 @@
     return p;
 }
 
+IUnknown* WINAPI AtlComQIPtrAssign(IUnknown** pp, IUnknown *p, REFIID riid)
+{
+    IUnknown *new_p = NULL;
+
+    TRACE("(%p %p %s)\n", pp, p, debugstr_guid(riid));
+
+    if (p) IUnknown_QueryInterface(p, riid, (void **)&new_p);
+    if (*pp) IUnknown_Release(*pp);
+    *pp = new_p;
+    return new_p;
+}
+
 
 HRESULT WINAPI AtlInternalQueryInterface(void* this, const _ATL_INTMAP_ENTRY* pEntries,  REFIID iid, void** ppvObject)
 {