CHANGED: version of depending modules that checks ENV before using it
ADDED: test subpbs node configuration
CHANGED: evaluation package is node dependent
CHANGED: call sub instead for string code

ADDED: better error messages when configuration attributes ar invalid
CHANGED: display location of subpbs definition, when handling subpbs node config, instead for "eval"
ADDED: better sub config example with proper digest generation
ADDED: test subpbs node configuration
Merge branch 'PACKAGE_CONFIG_via_sub'
ADDED: documentation for the PACKAGE_CONFIG example
ADDED: PACKAGE_CONFIG test
CHANGED: on build failure, only unlink files that are not "source"

Pbs "builds" C files. it's a nop but when the build fails, in this case when
a fork fails, Pbs unlinks %FILE_TO_BUILD. The change verifies if the %FTB
has been marked for _not_ having a digest generated (which is the method to
tag files that we consider source)