debuginfo: Improved stepping for if-expressions
pidigits resurected

Changes:
* default value when no args
* license
* removed libc printing
* use extra::bigint instead of handmade gmp binding
auto merge of #10555 : TeXitoi/rust/pidigits-resurected, r=alexcrichton

Changes:
* default value when no args
* license
* removed libc printing
* use extra::bigint instead of handmade gmp binding

The drawback is that it's 2 order of magnitude slower, the good news is that there is a good bench for extra::bigint.
auto merge of #10552 : michaelwoerister/rust/ifstepping, r=brson

This PR improves the single-stepping experience for if-expression (no more jumping into the *else* branch before entering the *then* branch, no more jumping to the end of the *else* branch after finishing the *then* branch). Unfortunately I don't know of a straight-forward way of writing automated tests for this. Suggestions welcome!
Use '..' as multi-field wildcard in enums and structs.
Use '..' as slice wildcard in vectors
auto merge of #10366 : brson/rust/ignore-patterns, r=alexcrichton

This replaces `*` with `..` in enums, `_` with `..` in structs, and `.._` with `..` in vectors. It adds obsolete syntax warnings for the old forms but doesn't turn them on yet because we need a snapshot.

#5830
libstd: Change all `~fn()`s to `proc`s in the standard library.

This makes `Cell`s no longer necessary in most cases.
libextra: Remove `~fn()` from libextra.
librustc: Remove the one use of `~fn()`
librustc: Convert `~fn()` to `proc()` everywhere.
libsyntax: Remove `~fn()` from the language