* complex.c (rb_complex_set_imag): Fix to properly set imag
	  of complex.

	* internal.h (RCOMPLEX_SET_IMAG): undef RCOMPLEX_SET_IMAG
	  instead of duplicated undef RCOMPLEX_SET_REAL.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@54899 b2dd03c8-39d4-4d8f-98ff-823fe69b080e