June 12th 2017 Toolchain Release

It's been a month since the last stable toolchain release, which seems like a
good time for another one. Here's the changes since the last release:

* GP-relative disassembly hints are working again.
* 32-bit BFDs can handle 64-bit objects.
* c.li, c.andi, and c.addiw disassembly correctly.

* A new "-mstrict-align" option is availiable, which enforces strict
  alignment. Without this argument the compiler assumes unaligned operations
  are slow instead of assuming they're illegal. This is meant to be used in
  machine-mode code on platforms that don't support unaligned accesses.
* Sub-XLEN PIC loads now extend correctly.
* An internal compiler error related to sub-word moves has been fixed.
* The initial GP generation cannot be relaxed.

* We are using a version based on 2.5.

* The prerequisite libraries are downloaded correctly again.
* There is a "--with-guile" flag
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