3.1.5_p2 currently unstable so will upgrade from 3.1.2_p10 to 3.1.3_p4

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/portage-stable/+/edf7e47afe85d9ff6ad4dc6c878e20876e241762

commit edf7e47afe85d9ff6ad4dc6c878e20876e241762
Author: Edward Hill <ecgh@chromium.org>
Date: Tue Jun 06 01:33:59 2017

mpfr: upgraded package to upstream

Upgraded dev-libs/mpfr to version 3.1.3_p4 on amd64, arm, x86

BUG= chromium:710089 
TEST=unit tests pass for pyro and x86-generic

Change-Id: Iaf2c9435029b6cc544e088d5c10bd49fbdea4185
Reviewed-on: https://chromium-review.googlesource.com/524236
Commit-Ready: Edward Hill <ecgh@chromium.org>
Tested-by: Edward Hill <ecgh@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch10
[rename] https://crrev.com/edf7e47afe85d9ff6ad4dc6c878e20876e241762/dev-libs/mpfr/mpfr-3.1.3_p4.ebuild
[add] https://crrev.com/edf7e47afe85d9ff6ad4dc6c878e20876e241762/dev-libs/mpfr/files/3.1.3/patch04
[modify] https://crrev.com/edf7e47afe85d9ff6ad4dc6c878e20876e241762/dev-libs/mpfr/Manifest
[rename] https://crrev.com/edf7e47afe85d9ff6ad4dc6c878e20876e241762/metadata/md5-cache/dev-libs/mpfr-3.1.3_p4
[add] https://crrev.com/edf7e47afe85d9ff6ad4dc6c878e20876e241762/dev-libs/mpfr/files/3.1.3/patch01
[add] https://crrev.com/edf7e47afe85d9ff6ad4dc6c878e20876e241762/dev-libs/mpfr/files/3.1.3/patch02
[add] https://crrev.com/edf7e47afe85d9ff6ad4dc6c878e20876e241762/dev-libs/mpfr/files/3.1.3/patch03
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch09
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch08
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch05
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch04
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch07
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch06
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch01
[modify] https://crrev.com/edf7e47afe85d9ff6ad4dc6c878e20876e241762/dev-libs/mpfr/metadata.xml
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch03
[delete] https://crrev.com/63797774382b15c5efbbcb4449f2195b6c8e8b9b/dev-libs/mpfr/files/3.1.2/patch02