Bug 835992 - Factor fennec-paths.sh out of fennec-{code-drop,copy-code}.sh.
Bug 835992 - Format Makefile variables in fennec-copy-code.sh.

Old:

VAR:=1.java 2.java

New:

VAR := \
  1.java \
  2.java \
  $(NULL)

This makes `hg diff` output smaller and hand-checkable.
Bug 835992 - Review comment: Remove bash specific directory handling.
Bug 835992 - Format Makefile variables in fennec-copy-code.sh. r=rnewman