Scaladoc links disambiguation issues

[scabug]

• when disambiguating between members the signatures should be post-processed to enable copy-paste:

Link.scala:22: warning: The link target "scala.concurrent.ExecutionContext$.fromExecutor(e:java\.util\.concurrent\.Executor*" is ambiguous. Several members fit the target:
(e: java.util.concurrent.Executor,reporter: Throwable => Unit): scala.concurrent.ExecutionContextExecutor in object ExecutionContext [chosen]
(e: java.util.concurrent.Executor): scala.concurrent.ExecutionContextExecutor in object ExecutionContext

Instead, the signatures should be:

[[fromExecutor(e:java\.util\.concurrent\.Executor,reporter:Throwable=>Unit): scala\.concurrent\.ExecutionContextExecutor]] in object ExecutionContext [chosen]
[[fromExecutor(e:java\.util\.concurrent\.Executor):scala\.concurrent\.ExecutionContextExecutor]] in object ExecutionContext

Steps necessary:

• escape dots and hashes
• remove whitespaces
• add the (full) path before

Another problem: in the crash course, escaping is incorrect:

Notes:
 - you can use any number of matching square brackets to avoid interference with the signature
 - you can use \\. to escape dots in prefixes (don't forget to use * at the end to match the signature!)
 - you can use \\# to escape hashes, otherwise they will be considered as delimiters, like dots.

We need:

• example for the first item
• \\. should be \.
• \\# should be \#

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-8723?orig=1 Reporter: @VladUreche

[eatkins]

Bump. It is a nightmare trying to disambiguate signatures for scaladoc and the current message is both not helpful for certain failures and wrong (see comment above about \\. vs \.).