Refactored example to Option.collect method.
Prevent SI-7905 by adding a test

The original issue was fixed already. This test is just for make sure.
Fixes cut sentences in the generated scaladocs

This commit changes all first sentences of library functions which
contain `i.e.` or `e.g.` and adds a `,` to prevent that the scaladoc
summary sentence is cut after this abbreviation.

This is possible as pull/3824 fixed how Scaladoc parses the first
sentence of a method description into a sumary sentence(now the first
sentence has to end with a dot followed by whitespace).

Only docs in the core library are changed (src/library/**/*.scala)
and only if they occur in the first sentence.

Review by @heathermiller
Merge pull request #3898 from adriaanm/jxcoder-issue-3861

Refactored example to Option.collect method.
Merge pull request #3918 from dgruntz/doc/firstSentenceFixes

Fixes cut sentences in the generated scaladocs
Merge pull request #3900 from kzys/jira-7905

Prevent SI-7905 by adding a test just in case
Bump version for 2.12.x

For this step, we still depend on _2.11 libraries (partest, xml,
parser-combinators).

After we release the first milestone of 2.12, we will update
versions.property to bootstrap to 2.12 dependencies.
WIP: trying to apply the Literal-based singleton types commit by @paulp to the master.
Fix non-working things.
Update check file.
Problems with null.
Update the check file.
This is needed for the tests to pass.
Added a macro to materialize an inhabitant for the singleton type.
Added a test with the Ranged class mentioned by @non.
Add inhabitant to the bincompat whitelist.
Marked potentiall places in code where constant type folding and singleton type inlining might occur.
Inlining functions with singleton result type.
More involved example with Ranged.
Needed for the tests to pass after adding the SingleInhabitant