The current version of the code incorrectly assumes that the lpszClass member of CREATESTRUCT passed with WM_CREATE will point to the same memory used for the CreateWindowEx class name parameter, and uses a pointer comparison to check for class name equality.
As a side effect of commit e41c255be6ba66d1eec7affe674b8cc7699226b8 "win32u: Use send_message_timeout for WM_CREATE and WM_NCCREATE" the CREATESTRUCT lpszClass member started pointing to different memory, breaking the current implementation of MCIWND_Create().
This commit fixes the problem by performing a proper, case-insensitive string comparison to determine class name equality.
Wine-bug: https://bugs.winehq.org/show_bug.cgi?id=53578
-- v4: msvfw32: Use window name to determine if window is created using MCIWndCreate. msvfw32: Test window creation with filename.