fixed regression in use of -f option to 'mx build'
mx: fix comments: jrelibrary is about the JRE, not the JDK

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extra : rebase_source : 9f93ea766eb54accdc7d78fed1b9aedf4c4fef6b
extra : histedit_source : d89838cc1ec0a422584d55613bda479013e42223
unswitching: check full SwitchNode structure

--HG--
extra : rebase_source : 3560623f4173226a1fc651a9729487ca7ebc71cd
extra : histedit_source : 7b8d12dd0a5bd768d7d5c5d190bfa98b152db831
Truffle: Add conditions to CompilerDirective accesses in FrameWithoutBoxing
Truffle/SourceAttribution:  NodeUtil.displaySourceAttribution() outut revised for legibility.
SL/SourceAttribution:  correct some omissions, and in particular add new node SLParenExpressionNode to represent a parenthesized expression; this is semantically neutral of course, but needed to account correctly for the text of such an expression (as opposed to its contents).