rpcrt4: Check that the input to RPCRT4_strndupW was not NULL before assuming that the string couldn't be allocated due to lack of memory.

Don't include platform-specific information when declaring the name of
the static import libary to build. Instead, add this information in
Makeimplib.rules.in.

pszHost should just be set to pszTargetName if pszTargetName doesn't
contain any other information.

wininet: Retrieve the maximum token length from the SSP and use a buffer of that length in calls to InitializeSecurityContextW.

Otherwise, InitializeSecurityContextW could run out of space with our
small, fixed buffer and fail.

When using SSPI, pass in a NULL identity in this case so that the SSP
can try to use cached credentials.

wininet: Make the reference count of WININETHANDLEHEADER thread-safe by using InterlockedIncrement/InterlockedDecrement.

Test if a P8 texture gets properly updated if there was a palette change while 
this texture wasn't bound to any stage.