widl: Only assign variables if not a string and only create a local variable if not a sized parameter.

Only assign variables if not a string and only create a local variable
if not a sized parameter. Fixes type mismatches in the generated code
due to differences in the algorithms between creating local variables
and using them.

widl: Initialise the temporary variable to 0 for parameters with more than one level of indirection.

Move handling of base type marshaling and unmarshaling to a separate
function and improve it to support return values.

- Add a function to generate the Ndr type calls.
- Fix a typo where the aligned buffer was added to itself, rather than
assigned.

Only write the buffer incrementing code for the marshaling and
unmarshaling phases - buffer sizing is handled elsewhere and freeing
isn't applicable.

Output the necessary sizing information for PHASE_BUFFERSIZE and
PHASE_FREE as well as PHASE_MARSHAL. Standardise this rule in a new
function.

- Generate eval's for enums that don't explicitly have one. This means
that enums written in header files won't match exactly what has been put
into the IDL file, but the numeric constat is the same and MIDL does a
similar thing.
- Replace constant lookups with eval->cval instead of lval.

De-reference parameters' types before deciding what to do with them.
Also dereference string parameters since they are immediately
dispatched to write_string_tfs when the string attribute is detected
without any further processing done on them.

Write definitions for MIDL_user_allocate and MIDL_user_free in the
header when writing out RPC interfaces to prevent compile failures in
the generated client/server code.

Only output code for non-object interfaces in client and server
generation and convert the while loops into for loops.

Avoids test failure when the current day happens to be the 31st...

Fix some string length calculations that didn't account for the
different sized characters with Unicode.

- Implement add disposition in CertAddCertificateContextToStore,
  rather than in each store.
- Add a few more tests.

These tests currently fail in Wine.

(based on a patch by Byeong-Sik Jeon).