check.h: remove obsolete header

Since we switched from autotools to Meson in commit
94592c1406, we don't need to include
`config.h` early to properly enable large file support.  Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.

This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.

src/archive/plugins/Bzip2ArchivePlugin.cxx

@@ -21,7 +21,6 @@
   * single bz2 archive handling (requires libbz2)
   */
 
-#include "config.h"
 #include "Bzip2ArchivePlugin.hxx"
 #include "../ArchivePlugin.hxx"
 #include "../ArchiveFile.hxx"