The isspace(3) man page is out of date

The isspace(3) man page incorrectly states that isspace(c) is defined
only when isascii(c) is true or c is EOF.

In fact, ISO C (going back to C89/C90) requires isspace(c) to work
correctly when c is either within the range of unsigned char or equal
to EOF (almost certainly 0..255 or -1 for systems supported by
newlib). The implementation of isspace() is correct; this is only a
documentation issue.

The other is*() functions work correctly and are documented correctly.

The following patch fixes this by copying the wording from isalpha().

I have *not* updated it to clarify just what "whitespace" means, but
it would probably be a good idea.

commit 932bca35395f3fc920b8d90b1f4bc07dc13efb93 (HEAD -> isspace-man-page)
Author: Keith Thompson <[email protected]>
Date:   2026-08-07 14:50:36 -0700

    Correct isspace(3) man page (copied wording from isalpha(3))

diff --git newlib/libc/ctype/isspace.c newlib/libc/ctype/isspace.c
index 0def2c0ce..784f4d7ae 100644
--- newlib/libc/ctype/isspace.c
+++ newlib/libc/ctype/isspace.c
@@ -18,7 +18,8 @@ SYNOPSIS
 DESCRIPTION
 <<isspace>> is a macro which classifies singlebyte charset values by table
 lookup.  It is a predicate returning non-zero for whitespace
-characters, and 0 for other characters.  It is defined only when
<<isascii>>(<[c]>) is true or <[c]> is EOF.
+characters, and 0 for other characters.  It is defined only if
+<[c]> is representable as an unsigned char or if <[c]> is EOF.

 <<isspace_l>> is like <<isspace>> but performs the check based on the
 locale specified by the locale object locale.  If <[locale]> is