Look at NI instead of PRI in ps output on Linux

The PRI field is the Linux kernel scheduling priority which is
different from the niceness of a process (which is what a system
adminitrator and policy-writer is likely to want to select upon). This
value is almost always larger than 20, so it isn't selectable if the
defined range per the documentation is -20,+20 anyway.
Redmine#2272: maparray() function
Redmine#2272: maparray() function style cleanup and return failure as needed
Out-of-tree builds broke again, fix.
Redmine#1735: classesmatching() function
Redmine#2178: add filestat() function and cfengine_stdlib.cf support
ifelse() function
add maparray() documentation
Adding yum_group package_method
Constify attributes.[ch]
Simplify checks for THIS_AGENT_TYPE == AGENT_TYPE_COMMON
Simplify seeding random number generator
Remove unused hash algorithms
Get rid of useless GetHash wrapper
Move [Xml]CompareToFile to cf-agent, not used in libpromises
Split files_hashes.h

This module contained two unrelated functionalities:

- File checksum database implementation (moved to cf-agent)
- Generic hash function utilities (left as is)
De-EvalContext-ify LoadFileAs{ItemList,XmlDoc}

Context was only used for calling cfPS, and all callers of those
functions either were not interested in setting promise outcome
or re-set promise outcome immediately anyway.
De-EvalContext-ify GetParentDirectoryCopy
De-EvalContext-ify mon_temp.c
De-EvalContext-ify IsNewerFileTree