Require and document using kernel headers from "make headers_install"

[Joseph S. Myers]

On Thu, 23 Feb 2012, Roland McGrath wrote:

> Incidentally, as a style note for the manual (not that you're introducing
> the problem newly here), originally we judiciously always used "the GNU C
> library" instead of any abbreviations in the manual.  We should restore

Is "GNU C library" or "GNU C Library" preferred?  Both are common (as is 
"GNU library", meaning glibc rather than a more generic description for 
all GNU libraries).

-- 
Joseph S. Myers
joseph@codesourcery.com