Fix for interactive docComment clearing in 2.11

Fixes #1000210, #1000453

finalizes eager site computation

absent return type of getHOverInfo breaks the play2 plugin

FIxing thread confinement in browserInput
more NSDNHO fixing in LocateSymbol

Cosmetics
Avoids memory leak of the inner BrowserInput(html, sym) through the outer pointer
Fix NpE in BrowserInput

Cosmetics

Fix NpE in getHoverInfo
Ports the branch to post-thread-safe-sourceFiles

cosmetics
Better test case compartmentation
Speed optimizations for findClassFile
Wrap main scaladoc comment in html paragraph tag.
Restore compilation: parseAndEnter has been removed.
Fix unexpanded variables in IndexedSeq reference from scala package object.
Type annotation to fix debug
Removing deprecations

Drive-by cleanups
Cleaner getHoverInfo2 on empty comment
Add parametric doc test
Centralize header code paths for hover/Completion