Import LinuxCNC source tree

tests/halcompile/extralib/extralib_test.comp

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+component extralib_test;
+pin in float theta;
+pin out float sin_;
+license "GPL";
+option userspace;
+option extra_link_args "-lm";
+;;
+#include <math.h>
+void user_mainloop(void) {
+    while(1) {
+        FOR_ALL_INSTS() sin_ = sin(theta);
+    }
+}