Make os.linesep default line_terminator in to_clipboard
closes #11720
- Make os.linesep default line_terminator in to_clipboard
- Add line_terminator kw to Series.to_csv
- Refactor to_clipboard

Observed/fixed problems in to_clipboard:
- try..except: pass
- excel=None, though it defaults to True
- several code paths with return
- sep argument could be passed via kwargs
- "other keywords are passed to to_csv" only if excel=True
- line_terminator kw isn't supported by Series to_csv

Is it ok to to change Series.to_csv api?
Also we need tests, right? But what does `# pragma: no cover` mean?

tests are in the obvious location: https://github.com/pydata/pandas/blob/master/pandas/io/tests/test_clipboard.py

pls add tests.
 Have no time today. will add asap
 ## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/13125?src=pr) is 84.11% (diff: 80.00%)

> Merging [#13125](https://codecov.io/gh/pydata/pandas/pull/13125?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will decrease coverage by **1.12%**

``` diff
@@             master     #13125   diff @@
==========================================
  Files           140        138     -2   
  Lines         50563      50388   -175   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
- Hits          43103      42386   -717   
- Misses         7460       8002   +542   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [37f95ce...255895f](https://codecov.io/gh/pydata/pandas/compare/37f95cef85834207db0930e863341efb285e38a2...255895fe35afad2a249637c526fea92db1b40fac?src=pr)
 - [x] compatibility fixes
- [x] tests
 can you rebase / update?
 I'll look into it on monday.
 Rebased.
 same comment as on the issue. https://github.com/pandas-dev/pandas/commit/4a1a330343f31fc8ca62b98a84978475968cba9c updated the vendored pyperclip.

is this PR still relevant? closing, but if you want to update / respond we can reopen