[SV 64822, SV 36486] Fix appending to a pattern specific variable
* NEWS: Clean up
[SV 64803] Set origin for unmodified variables after -e
* tests/test_driver.pl: Add cd to the .run output file
Replace target_var boolean with enum variable_scope
* doc/make.texi: Grammar improvements.
Remove unnecessary parsing during makefile read
Create a common method for skipping variable references