Fix shared library names on OSX

- OSX format is libname.major.minor.patch.dylib
- closes #666

Makefile

@@ -345,9 +345,16 @@ SHARED_MAJOR = $(ROCKSDB_MAJOR)
 SHARED_MINOR = $(ROCKSDB_MINOR)
 SHARED_PATCH = $(ROCKSDB_PATCH)
 SHARED1 = ${LIBNAME}.$(PLATFORM_SHARED_EXT)
+ifeq ($(PLATFORM), OS_MACOSX)
+SHARED_OSX = $(LIBNAME).$(SHARED_MAJOR)
+SHARED2 = $(SHARED_OSX).$(PLATFORM_SHARED_EXT)
+SHARED3 = $(SHARED_OSX).$(SHARED_MINOR).$(PLATFORM_SHARED_EXT)
+SHARED4 = $(SHARED_OSX).$(SHARED_MINOR).$(SHARED_PATCH).$(PLATFORM_SHARED_EXT)
+else
 SHARED2 = $(SHARED1).$(SHARED_MAJOR)
 SHARED3 = $(SHARED1).$(SHARED_MAJOR).$(SHARED_MINOR)
 SHARED4 = $(SHARED1).$(SHARED_MAJOR).$(SHARED_MINOR).$(SHARED_PATCH)
+endif
 SHARED = $(SHARED1) $(SHARED2) $(SHARED3) $(SHARED4)
 $(SHARED1): $(SHARED4)
 	ln -fs $(SHARED4) $(SHARED1)