* array.c, string.c: use ruby_xsizedfree() and ruby_xsizedrealloc().
* internal.h (SIZED_REALLOC_N): define a macro as REALLOC_N().



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43332 b2dd03c8-39d4-4d8f-98ff-823fe69b080e