Clarify that translated translation units are linked to form a program.

Possible resolution:

1. Change in 5.2 [lex.phases] paragraph 8 as follows:

   8. Translated translation units are combined, and all external entity references are resolved (6.7 [basic.link]). Library components are linked to satisfy external references to entities not defined in the current translation. All such translator output is collected into a program program image which contains information needed for execution in its execution environment.

2. Change in 6.7 [basic.link] paragraph 1 as follows:

   A program consists of one or more translation units (5.1 [lex.separate]) linked together. A translation unit consists of a sequence of declarations. ...