xkbcomp: Stricter handling of default map include Before this commit, including a *default* map, i.e. without an explicit section name (e.g. `include "au"` vs `include "au(basic)"`) would match the first section of the first matching file in the XKB include paths, even if this section is not an *explicit* default map (i.e. tagged with `default`) but an *implicit* default map (i.e. the first map of the file, i.e. a weak match). It makes user configuration risky: say a user wants to create a custom version `au(custom)` of the `au` layout: - `./config/xkb/symbols/au`: custom layout in section “custom”. - `/usr/share/X11/xkb/symbols/au`: system layout, with *default* section “basic”. In this setup *any* layout that imports the default map from `au` would in fact import the *implicit* default map `au(custom)` instead of the *explicit* default map `au(basic)`. This incorrect behavior may thus break setups with multiple layouts. This is especially true for symbols files such as: `pc`, `us` or `latin`. Fixed by trying harder to found the exact default map, defaulting to the old behavior (weak match) only if no *explicit* default map (exact match) has been found in the XKB include paths.