Closes #8943 COMPAT: periods needs coercion to np.int64

In _generate_regular_range, we explicitly cast `periods` to np.int64 to prevent
overflow in the function tseries.index._generate_regular_range.
Note: we don't bother casting it for the function call generate_range since
there's no danger of overflow in that function.
Merge pull request #9078 from Garrett-R/fix_8943

Closes #8943:  COMPAT: periods needs coercion to np.int64
overflow bug in multi-index when checking for duplicates
Merge pull request #9101 from behzadnouri/mi-dups

overflow bug in multi-index when checking for duplicates
BUG in read_csv when using skiprows on a file with CR line endings with the c engine. #9079
BUG: Bug in DatetimeIndex iteration, related to (GH8890), fixed in (GH9100)
Fixes GH9099: Support simultaneous copy and dtype args in DataFrame init
TST: sql skip tests at class level if database is not available
Merge pull request #9104 from jreback/dti_iteration

BUG: Bug in DatetimeIndex iteration, related to (GH8890), fixed in (GH9100)
API: Index.duplicated should return np.array
Merge branch 'master' of https://github.com/mairas/pandas into mairas-master

Conflicts:
	doc/source/whatsnew/v0.16.0.txt
Merge branch 'duplicated2' of https://github.com/sinhrks/pandas into sinhrks-duplicated2
Merge branch 'trailing_spaces_fix' of https://github.com/selasley/pandas into selasley-trailing_spaces_fix

Conflicts:
	doc/source/whatsnew/v0.16.0.txt
SQL: fix type conversion for Timestamp object typed columns (GH9085)
Merge pull request #9110 from jorisvandenbossche/sql-testing-skipclass

TST: sql skip tests at class level if database is not available
Merge pull request #9109 from jorisvandenbossche/sql-timestamp-object

SQL: fix type conversion for Timestamp object typed columns (GH9085)
fix an nbviewer link in tutorials

some escape characters snuck in there that cause the URL to be invalid
Merge pull request #9120 from minrk/nbviewer-link

fix an nbviewer link in tutorials
unstack with nan in the index
Merge pull request #9061 from behzadnouri/nan-pivot

pivot & unstack with nan in the index