malloc-fail: Handle more malloc failures in schema code These issues can only arise after a memory allocation failed. - WXS_ADD_*: Add NULL check and raise error - XML_SCHEMA_*: Make macros safe - xmlSchemaParseUnion: Fix leak, raise error, commit after success to avoid memory corruption - xmlSchemaVAddNodeQName: Restore nbItems after partial success, raise error - xmlSchemaIDCAcquireTargetList: Raise error - xmlSchemaXPathProcessHistory: Handle errors - xmlSchemaIDCFillNodeTables: Fix leak - xmlSchemaCheckCVCIDCKeyRef: Handle errors - xmlSchemaVPushText: Reset flag to avoid memory corruption - xmlSchemaNewValidCtxt: Handle errors - xmlSchemaVDocWalk: Fix leak - xmlSchemaInitBasicType: Handle error - xmlSchemaCleanupTypesInternal: Fix null deref - xmlSchemaWhiteSpaceReplace: Handle error - xmlSchemaParseUInt: Handle error - xmlSchemaValAtomicType: Fix leak, handle error - xmlSchemaDateNormalize: Fix leak