* gc.c (wmap_final_func): fix memory size shortage when realloc wmap.
  Fix SEGV during finilize of WeakRef on Solaris (though the SEGV
  could occur on all OS/platforms). [ruby-dev:48779] [Bug #10646]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48999 b2dd03c8-39d4-4d8f-98ff-823fe69b080e