Only consider "@repo" notation for relative paths
Only consider "@repo" notation for relative paths

This does not change newt's behavior, but it allows a future change to
be implemented.  If a path is absolute (i.e., it starts with '/'), do
not perform any relative path fixups on it.

This allows the config-read functions to be used before the project has
been loaded.  Prior to this commit, all read functions attempted to
retrieve the project's base directory so that relative paths could be
fixed up.

apache/incubator-mynewt-newt,apache/incubator-mynewt-newt