rb_call_info_t: shrink to 96 bytes from 104 bytes on 64-bit

This keeps ci->flag and ci->aux.index consistent across 32-bit
and 64-bit platforms.

ci->flag: VM_CALL_* flags only use 9 bits, currently
ci->aux.index: 2 billion ivars per class should be enough for anybody

This saves around 50K allocations on "valgrind ruby -e exit" on x86-64
before:
  total heap usage: 48,122 allocs, 19,253 frees, 8,099,197 bytes allocated
after:
  total heap usage: 48,069 allocs, 19,214 frees, 8,047,266 bytes allocated

* vm_core.h (rb_call_info_t): ci->flag becomes 32-bit unsigned int
  ci->index becomes a 32-bit signed int (from signed long).
  Reorder for better packing on 64-bit, giving an 8 byte reduction
  from 104 to 96 bytes for each ci.

* compile.c (new_callinfo, setup_args, iseq_compile_each,
  iseq_build_from_ary_body): adjust for type changes

* vm_insnhelper.c (vm_getivar): ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47509 b2dd03c8-39d4-4d8f-98ff-823fe69b080e