Declare ocsigenserver as a 1.2 package

it uses an (uncommented) dev-repo field that triggered a warning on 1.1
this will also serve as a test of the new redirection/rewriting repo rules for 1.1 vs 1.2
Travis script: some changes

- test the specific changed package versions
- use autoremove
- simpler check for package availability
- replace 'grep | sed | grep | awk' with a single 'sed'
Update travis script to apply opam version compat before testing on <1.2
lambda-term 1.7
Update MD5 sum for fixed release of Slacko

Forgot to set the proper version in _oasis in the original upload, this
one has the proper information.
Mark ppx_tools as unavailable on 4.03.
add chamo 2.03
chamo 2.03: add dependency to (now standlone) camlp4
add xmldiff 0.5.0
more cosntraints on lablgtk and ocaml for chamo 2.01 and 2.02
camlp4 4.02.1+1
Merge pull request #2908 from diml/camlp4-4.02.1+1

camlp4 4.02.1+1
Merge pull request #2907 from zoggy/master

Add chamo 2.03
Merge pull request #2906 from whitequark/ppx_tools.compat

Mark ppx_tools as unavailable on 4.03
Merge pull request #2903 from Leonidas-from-XIV/bugfix/rerelease-slacko-0.10.0

Update MD5 sum for fixed release of Slacko
Merge pull request #2902 from diml/lambda-term-1.7

lambda-term 1.7
Added exn-source v0.1
Fixed ocamlfind dependency
camomile.0.8.5: decouple from camlp4
Revert "Mark ppx_tools as unavailable on 4.03"