package.bashrc: per profile, per-package bashrc mechanism

Profiles can define per-package bashrc files to be sourced before emerging.
Each line in package.bashrc must be an atom name then a list of space-delimited
bashrc files (stored in $profile/bashrc/).

(cherry picked from commit 803dafc462027d6015721f40513abb5f57dc1178)

Change-Id: Iae234b08d14fa63cdb3d973c2fb85430e88bf3f0
Reviewed-on: https://chromium-review.googlesource.com/225513
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
9 files changed