Instead of having the IconTheme have a hashtable that owns
individual strings and then IconThemeDirSize have a similar
hash (but with the strings owned by the other hash), we
have a consecutive memory chunks where we store the icon names
and then the hashtable has pointers into this.
This means we can avoid a bunch of individual strdup()s in a
way that is less fragmented and wastes less space. Additionally,
since we do an initial lookup anyway we have the internalized
icon name during lookup which means we can use g_direct_hash/equal
instead of g_str_hash/equal making the lookup faster too.
We expose no API to get at any colors for drawing symbolics, so we
shouldn't have APIs to draw with them.
Apart from that, those APIs look like a box of crayons, not like an
icontheme.
This is sometimes needed, and calling into actual icon theme
code just for it is confusing - the resulting icon does not
depend on the icon theme at all.
https://bugzilla.gnome.org/show_bug.cgi?id=760536
