6537506: Provide a mechanism for specifying Java-level USDT-like dtrace probes

Initial checkin of JSDT code

Reviewed-by: acorn, sbohne

hotspot/src/share/vm/asm/codeBuffer.hpp

@@ -36,6 +36,7 @@ public:
                  Verified_Entry,
                  Frame_Complete, // Offset in the code where the frame setup is (for forte stackwalks) is complete
                  OSR_Entry,
+                 Dtrace_trap = OSR_Entry,  // dtrace probes can never have an OSR entry so reuse it
                  Exceptions,     // Offset where exception handler lives
                  Deopt,          // Offset where deopt handler lives
                  max_Entries };