[docs] Better index entry for encoding declarations (issue 18628)

[mansam at csh.rit.edu]

http://bugs.python.org/review/18628/diff/11570/Doc/reference/lexical_analysis.rst
File Doc/reference/lexical_analysis.rst (right):

http://bugs.python.org/review/18628/diff/11570/Doc/reference/lexical_analysis.rst#newcode79
Doc/reference/lexical_analysis.rst:79: .. index:: source character set,
encoding declarations (source file)
On 2014/04/14 20:00:27, eric.araujo wrote:
> Minor: I would use the singular here, “declaration” (there is only one
in a
> file).

I used the plural to be consistent with the section header above, but I
am happy to change it if you like.

http://bugs.python.org/review/18628/