GB022 04.01Allow "import" for accessing standard library names

[wg21bot]

Allow access to standard library names via import
[intro.compliance] 4.1 p5
"The names defined in the library have namespace scope (9.7). A C++ translation unit (5.2) obtains access to these names by including the appropriate standard library header (15.2)."

Proposed change:
Add that standard library names can also be accessed by importing the appropriate header unit.:
… library header (15.2) or importing the appropriate standard library named header unit (10.3), [headers] 16.5.1.2 p4.

[jensmaurer]

Given [using.headers], this is an editorial fix. Retargeting.

[jensmaurer]

Accepted with modification.