Dump PostgreSQL primary key with custom function as a default.

For example, if use pgcrypto extension in PostgreSQL 9.4 beta 1, where
uuid-ossp extension isn't available for moment of writing, and thus to
use a gen_random_uuid() method as a primary key default.

In this case schema dumper wasn't able to correctly reconstruct
create_table statement and lost primary key constraint on schema load.

Fixes #16111.
Fix typos like `a html` to `an html` and 'an mail' to 'an email'. [ci skip]
Merge pull request #16155 from mechanicles/fix-typos

[ci skip] Fix typos like `a html` to `an html` and 'an mail' to 'an email'.
Format pass on 4.2 release notes [ci skip]

*   Leave two blank lines between sections/packages for readibility.

*   Always indent bullet points with four spaces. This allows multi-paragraph
    points to align properly (see #16103), and it is the same as the format we
    already use in CHANGELOGs. Doing this consistently sets an easy precedent
    for future contributors to follow.

*   Always put the PR/commit link on its own line in the source. If the bullet
    point spans multiple paragraphs, put it on its own paragraph at the end.

[Godfrey Chan & Juanito Fatas]
[ci skip] Little bit doc code improvement.
Merge pull request #16156 from mechanicles/document-improvement

[ci skip] Improve documentation consistency for ActiveModel::Errors
Merge pull request #16127 from Envek/fix_16111

Dump PostgreSQL primary key with custom function as a default.
Stash original path in `ShowExceptions` middleware

`ActionDispatch::ShowExceptions` overwrites `PATH_INFO` with the status code
for the exception defined in `ExceptionWrapper`, so the path the user was
visiting when an exception occurred was not previously available to any custom
exceptions_app.

The original `PATH_INFO` is now stashed in
`env["action_dispatch.original_path"]`.
Address ORA-00972: identifier is too long when tested with Oracle
by using shorter attribute names.
Merge pull request #16167 from yahonda/ora972_faces

Address ORA-00972: identifier is too long when tested with Oracle
Merge pull request #16168 from greysteil/stash-path-info

Stash original path in `ShowExceptions` middleware