[docs] Index "code object" and link to code object definition (issue 15476)

[vadmium+py at gmail.com]

https://bugs.python.org/review/15476/diff/17455/Doc/library/marshal.rst
File Doc/library/marshal.rst (right):

https://bugs.python.org/review/15476/diff/17455/Doc/library/marshal.rst#newcode20
Doc/library/marshal.rst:20: object: code
I think the “code” index point(s) should be attached to the following
paragraph, about support of code and other objects in marshal.

This paragraph is about the relationship with the pickle and shelve
modules.

https://bugs.python.org/review/15476/diff/17455/Doc/library/stdtypes.rst
File Doc/library/stdtypes.rst (right):

https://bugs.python.org/review/15476/diff/17455/Doc/library/stdtypes.rst#newcode4445
Doc/library/stdtypes.rst:4445: 
The generated HTML seems to work better if you include the “..
_bltin-code-objects:” label _after_ the index code, instead of before.
Otherwise, #bltin-code-objects points to the end of the previous
section, rather than into the new section.

https://bugs.python.org/review/15476/