MRUBY_OBJECT_HEADER is always used with `;', but, in the definition of a struct, you cannot include any statement except declarations, even if the statement is void statement.

In mruby.h, there is no definitions of RSTRING_* here, so cannot compile if the compiler is not GCC.

Add space after comma 

Fix spelling

fix Makefile: quoted CC/LL are heap up to each Makefiles.