include/c: remove a duplicate include

Also tweak some comments.

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
include/carefulputc: remove a duplicate include

Also tweak a comment.

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
lib/colors: change an include to a local one

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
include/c: do not gettextize a wordless string

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
ipcs: do not gettextize wordless strings

Also tweak a few parts of the usage message.

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
ionice: add a missing error message

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
textual: slice up and standardize the usage text of ionice

Done for ease of translation and maintenance.  Also improve the
clarity of some of the descriptions, and of one error message.

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
docs: grammarize the usage howto

Signed-off-by: Benno Schulenberg <bensberg@justemail.net>