mingw: Missing __lock_file in gtk dll
Submitted by Jan-Michael Brummer
With the commit aa352168 config.h.win32.in: Update for _lock_file() the lock_file handling in gtk has changed for windows. As mingw does not offer this functionality, the cross compiled library complains about missing __lock_file.
Reverting this commit solves this issue. Would be good to set this setting only for native compiles and leave the cross compiler with the old setting.