Until now, it was not possible to query the engine whether its
build configuration contained debugging support. This commit adds
the `JERRY_FEATURE_DEBUGGER` label to `jerry_feature_t` and extends
`jerry_is_feature_enabled` to support the new feature flag.
Additionally, the command line tool `jerry` was enhanced to report
a warning when invoked with `--start-debug-server` but linked to a
non-debuggable engine.
JerryScript-DCO-1.0-Signed-off-by: Akos Kiss [email protected]