Merge xgen and soft deprecate existing behaviours
Rename some Makefile targets. Closes #2274

kernel -> core
test_kernel -> test_stdlib
Merge pull request #2275 from alco/makefile-rename-kernel

Rename some Makefile targets. Closes #2274
core -> stdlib in makefile
Properly handle non-boolean values for boolean options
Add more sanity-check tests for OptionParser
Don’t ignore values for ‘--no-*’ options
Format OptionParser tests more nicely