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](https://github.com/scala/scala/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)
by this pull request and only if they occur in a first sentence.

Review by @heathermiller