fixed the unit test builds failure

fixed the following build error

/home/uchida/src/taglib/tests/test_flac.cpp: In member function ‘void TestFLAC::testInvalid()’:
/home/uchida/src/taglib/tests/test_flac.cpp:242: error: reference to ‘uint’ is ambiguous
/usr/include/sys/types.h:153: error: candidates are: typedef unsigned int uint
/home/uchida/src/taglib/tests/../taglib/toolkit/taglib.h:66: error:                 typedef unsigned int TagLib::uint
/home/uchida/src/taglib/tests/test_flac.cpp:242: error: reference to ‘uint’ is ambiguous
/usr/include/sys/types.h:153: error: candidates are: typedef unsigned int uint
/home/uchida/src/taglib/tests/../taglib/toolkit/taglib.h:66: error:                 typedef unsigned int TagLib::uint
/home/uchida/src/taglib/tests/test_flac.cpp:243: error: reference to ‘uint’ is ambiguous
/usr/include/sys/types.h:153: error: candidates are: typedef unsigned int uint
/home/uchida/src/taglib/tests/../taglib/toolkit/taglib.h:66: error:                 typedef unsigned int TagLib::uint
/home/uchida/src/taglib/tests/test_flac.cpp:243: error: reference to ‘uint’ is ambiguous
/usr/include/sys/types.h:153: error: candidates are: typedef unsigned int uint
/home/uchida/src/taglib/tests/../taglib/toolkit/taglib.h:66: error:                 typedef unsigned int TagLib::uint