Make CFLAGS overridable.

If $CFLAGS is not last in the assignment, then you cannot override
flags like -O2.
tests/acceptance: improve default_check_strcmp and add default_check_regcmp
Redmine#3122: acceptance test for list interpolation order
respect CFENGINE_COLOR=1 environment setting
tests: make 01_vars/02_functions/00[12].cf work under archlinux
Merge pull request #1315 from cdituri/core/make-tests-work-under-archlinux

tests: make 01_vars/02_functions/00[12].cf work under archlinux
Follow /bin/sh style of variable exporting.
remove group meta tag from variables, they should have their own group
proper group name for variables
tests/acceptance: s/difference/mismatch/
IsDir2().
Fixed documentation, added TODO.
remove inventory tag from classes that are covered by variables
Promise constification.
add windows roles as class groups (workstation,server,domain controller)
add vm host as class groups (xen,vmware,openvz,oracle)
CFEngine roles as inventory (just policy_server for now)
Merge pull request #1318 from estenberg/feature/inventory-groups

Inventory groups for reporting
Merge pull request #1313 from tzz/feature/color-from-environment

respect CFENGINE_COLOR=1 environment setting
Redmine#2100: acceptance test for chmod on an immutable file