[Rd] doc buglet: misleading description in ?source

[Deepayan Sarkar]

[with current r-devel]

source() works fine with connections, as explained in the entry for 
'file' and in the 'Details' section. However, the description is 
misleading, saying that:

    'source' causes R to accept its input from the named file (the
     name must be quoted). Input is read from that file until the end
     of the file is reached. <...>

Deepayan