extconf.rb in stackprof-0.2.0

- old
+ new

@@ -1,2 +1,9 @@
 require 'mkmf'
-create_makefile('stackprof')
+if have_func('rb_postponed_job_register_one') &&
+   have_func('rb_profile_frames') &&
+   have_func('rb_tracepoint_new') &&
+   have_const('RUBY_INTERNAL_EVENT_NEWOBJ')
+  create_makefile('stackprof')
+else
+  fail 'missing API: are you using ruby 2.1+?'
+end