Consider rendering prefix when pretty printing values in the REPL

[lihaoyi]

Previously the initial val res0: Seq[Int] = was not considered, so the pretty-printed value when appended to it could over-run the 100-column limit of the REPL. This PR properly takes the last line of the prefix (which can have multiple lines) and passes it to PPrinter.apply's initialOffset so the first line considers the prefix and wraps earlier as necessary

Tested manually with Seq.tabulate(22)(identity). The single-line output (below) is 104 characters, exceeding the 100 char default limit. With this PR, it properly wraps, while without this PR it doesn't, and you instead need to go all the way up to Seq.tabulate(27)(identity) for it to wrap

val res0: Seq[Int] = List(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)

[Gedochao]

LGTM

[lihaoyi]

@tgodzik not sure if you need to do anything when merging, but last PR you merged you didn't squash it (8ac4db2) so do remember to move the dropdown from Merge to Squash and Merge and make sure the merge message is the PR description (should be automatic but need to make sure)

[tgodzik]

@tgodzik not sure if you need to do anything when merging, but last PR you merged you didn't squash it (8ac4db2) so do remember to move the dropdown from Merge to Squash and Merge and make sure the merge message is the PR description (should be automatic but need to make sure)

Och damn, I was sure I was doing squash. Sorry about that

[tgodzik]

LGTM