Merge pull request #1526 from OCamlPro/fixes

Some fixes, and call the solver on 'opam reinstall'
better error reporting on action failure
Continue after failing to auto-update pinned packages
Add travis run of opam-rt without external solver
Patch dose to remove hard failure cases
Pass orphans to opamSolver.resolve
Merge pull request #1529 from OCamlPro/fixed-heuristic-rt

Adds opam-rt+heuristic to travis, and fix it
Modernise README a bit
Fixed bug with orphan packages causing Not_found in the solver
Merge pull request #1533 from OCamlPro/doc-orphans

change README and fix bug related to orphans and the solver
Fixed latex error in dev man

made Thomas disappear, sorry !
opam_installer.sh: fix wget emulation by cURL.
Merge pull request #1537 from OCamlPro/fix-dev-man-authors

Fixed latex error in dev man
Ensure switches can't be created in conflicting directories
Display all depext tags with 'opam list --external' and no argument
opam_install.sh: revive error() that works well under -e.

Notes on scoping/evaluation rules of POSIX SH: only passing
bar:$3 as foo:$1 is problematic in the below script.

! /bin/sh

set -e

foo () {
    echo "x==[$x] y==[$y] \$1==[$1]"
}

bar () {
    x=$1
    y=$2
    foo $3
}

bar "a b c" "1 2 3" "P Q R"
Merge pull request #1538 from nodakai/fix-opam_install.sh

opam_installer.sh: fix wget emulation by cURL.
Merge pull request #1541 from OCamlPro/easy-check-depext

Display all depext tags with 'opam list --external' and no argument
Exec through an exception to make sure everything is closed properly

Closes #1535

Also sets the CLOEXEC flag on locks, to make sure they're not inherited
Disable the O_CLOEXEC flag for compat with OCaml 3.12

Would be safer with it, but the rest of the fix should be enough for the case at hand