-static size_t +static size_t _GL_ATTRIBUTE_PURE gl_tree_size (gl_list_t list)
Although changes like these don't break anything, I generally don't bother doing them if only older GCCs warn about a missing attribute, under the theory that people stuck with older compilers can build with --disable-gcc-warnings and it lessens the maintenance burden if we don't bloat the code with obvious detail that a decent compiler should deduce automatically.
