/usr/include/gimp-2.0/libgimpbase/ is in libgimp2.0-dev 2.6.12-1ubuntu1.4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/gimp-2.0/libgimpbase/gimpbase.h
/usr/include/gimp-2.0/libgimpbase/gimpbaseenums.h
/usr/include/gimp-2.0/libgimpbase/gimpbasetypes.h
/usr/include/gimp-2.0/libgimpbase/gimpchecks.h
/usr/include/gimp-2.0/libgimpbase/gimpcpuaccel.h
/usr/include/gimp-2.0/libgimpbase/gimpdatafiles.h
/usr/include/gimp-2.0/libgimpbase/gimpenv.h
/usr/include/gimp-2.0/libgimpbase/gimplimits.h
/usr/include/gimp-2.0/libgimpbase/gimpmemsize.h
/usr/include/gimp-2.0/libgimpbase/gimpparam.h
/usr/include/gimp-2.0/libgimpbase/gimpparasite.h
/usr/include/gimp-2.0/libgimpbase/gimpparasiteio.h
/usr/include/gimp-2.0/libgimpbase/gimprectangle.h
/usr/include/gimp-2.0/libgimpbase/gimpsignal.h
/usr/include/gimp-2.0/libgimpbase/gimpunit.h
/usr/include/gimp-2.0/libgimpbase/gimputils.h
/usr/include/gimp-2.0/libgimpbase/gimpversion.h