Improve performance of creating Hash object

When generate Hash object, the heap area of st_table will be always allocated in internally
and seems it take a time.

To improve performance of creating Hash object,
this patch will reduce count of allocating heap areas for st_table by reuse them.

	Performance of creating Hash literal -> 1.53 times faster.

[Fix GH-1766] [ruby-core:84008] [Feature #14146]

### Environment

* OS : macOS 10.13.1
* CPU : 1.4 GHz Intel Core i7
* Compiler : Apple LLVM version 9.0.0 (clang-900.0.39)

### Before

$ ./miniruby -v -I. -I../benchmark-ips/lib ~/tmp/bench/literal.rb
ruby 2.5.0dev (2017-11-28 hash 60926) [x86_64-darwin17]
Warming up --------------------------------------
        Hash literal    51.544k i/100ms
Calculating -------------------------------------
        Hash literal    869.132k (± 1.1%) i/s -      4.381M in   5.041574s

### After

$ ./miniruby -v -I. -I../benchmark-ips/lib ~/tmp/bench/literal.rb
ruby 2.5.0dev (2017-11-28 hash 60926) [x86_64-darwin17]
Warming up --------------------------------------
        Hash literal    63.068k i/100ms
Calculating -------------------------------------
        Hash literal      1.328M (± 2.3%) i/s -      6.685M in   5.037861s

### Test code

require 'benchmark/ips'

Benchmark.ips do |x|
  x.report "Hash literal" do |loop|
    count = 0
    while count < loop
      hash = {foo: 12, bar: 34, baz: 56}

      count += 1
    end
  end
end

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61309 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 0 deletions

diff --git a/inits.c b/inits.c
index 5822f04cab..2c2ef17e2a 100644
--- a/inits.c
+++ b/inits.c
@@ -16,6 +16,7 @@
 void
 rb_call_inits(void)
 {
+    CALL(st);
     CALL(Method);
     CALL(RandomSeedCore);
     CALL(sym);