[coq.8.4pl1] Replace version 8.4 by 8.4pl1

Fix a compilation issue of Coq 8.4 with lablgtk 2.16.0
Fix compilation issue with bin/coqtop.byte.
 Cf. https://sympa.inria.fr/sympa/arc/coq-club/2013-01/msg00067.html
[coq.8.4pl1] fix: the target bin/coqide.byte override CAML_LD_LIBRARY_PATH

The error was:
OCAMLC -o bin/coqide.byte
File "ide/coqide_main.ml4", line 1:
Error: Error on dynamically loaded library: dlllablgtk2.so: dlllablgtk2.so: cannot open shared object file: No such file or directory
Merge pull request #303 from bobot/master

update coq8.4 to coq8.4pl1 and fix build problems