input: repair key combos containing both explicit modifier and shifted symbol

If a user-provided key combo contains both an explicit modifier, and
the shifted symbol it produces, replace the symbol with its un-shifted
version.

Example: Control+Shift+U contains both ‘Shift’, and ‘U’, where ‘Shift’
is the modifier that shifts ‘u’ to ‘U’.

Such modifiers are “consumed”, i.e. filtered out, when matching key
combos. As such, Control+Shift+U will never trigger since we’ll never
be able to match the consumed modifier ‘Shift’.

The above combo can be written in two ways:

- Control+U
- Control+Shift+u

To be able to detect that Control+Shift+U is an invalid combination,
we need to check all *shifted* symbols for all key *codes*.

Once we’ve detected a shifted symbol (and where it differs from the
un-shifted symbol), we loop all modifier sets that produce the shift
level where our shifted symbol is. For each such set, check if it
intersects with the user-provided key combo’s modifier set.

If there is an intersection, it means the user provided a key combo
containing a modifier and symbol, such that the modifier is consumed
when the symbol is produced.

In this case, we replace the symbol with its un-shifted version.

config.c

@@ -1191,6 +1191,7 @@ parse_key_combos(struct config *conf, const char *combos, key_combo_list_t *key_
             key++;  /* Skip past the '+' */
         }
 
+#if 0
         if (modifiers.shift && strlen(key) == 1 && (*key >= 'A' && *key <= 'Z')) {
             LOG_WARN(
                 "%s:%d: [%s]: %s: %s: "
@@ -1204,7 +1205,7 @@ parse_key_combos(struct config *conf, const char *combos, key_combo_list_t *key_
                 path, lineno, section, option, combo);
             *key = *key - 'A' + 'a';
         }
-
+#endif
         /* Translate key name to symbol */
         xkb_keysym_t sym = xkb_keysym_from_name(key, 0);
         if (sym == XKB_KEY_NoSymbol) {