Improve testing of new shared pointer

Adding measure of coverage. Need to move some codes outside the main C file, to avoid polluting the measure of the coverage by some functions we don't need to measure.

tests/test-mshared-ptr.h

@@ -0,0 +1,7 @@
+// Header for coverage purpose
+// Expand here all code that shall not be measured in coverage.
+// Since the functions are not declared as static inline, their coverage is measured
+SHARED_PTR_DEF_EXTERN_AS(shared_int, SharedInt, int, M_BASIC_OPLIST)
+SHARED_PTR_DEF_EXTERN_AS(shared_double, SharedDouble, double, M_OPEXTEND(M_BASIC_OPLIST, TYPE(double)))
+SHARED_PTR_DEF_EXTERN(shared_array, array_t)
+SHARED_PTR_DEF_EXTERN(shared_array_str, array_str_t, ARRAY_OPLIST(array_str, M_STRING_OPLIST))