Add `assert_match` and `assert_not_match`

Change modifier to `MRB_INLINE` from `static inline`

Use `MRB_ASPEC_XXX()` macro in `codedump()`

Commented out `String#scan` because it is not implemented yet

Expand `BOXWORD_SET_VALUE()` macro in `include/mruby/boxing_word.h`

In `SET_OBJ_VALUE()`, branch isn't removed because `switch` condition isn't
constant expression.

Fixes the twiddle wakka comparison algorithm

Add type check (conversion) in `String#[]=`

Add `mrb_true_p()` and `mrb_false_p()` macro functions

Before this patch:

  'a'[0] = 1        #=> 1
  'a'[:a] = '1'     #=> ArgumentError
  'a'[:a, 0] = '1'  #=> ArgumentError
  'a'[0, :a] = '1'  #=> ArgumentError
  'a'[0, 1] = 1     #=> 1

After this patch / Ruby:

  'a'[0] = 1        #=> TypeError
  'a'[:a] = '1'     #=> TypeError
  'a'[:a, 0] = '1'  #=> TypeError
  'a'[0, :a] = '1'  #=> TypeError
  'a'[0, 1] = 1     #=> TypeError

Remove duplicated `include Comparable` in `mrblib/string.rb`

Add `Array#sample` test

And simplify tests for `Array#shuffle` and `Array#shuffle!`.

Avoid potential zero size array declaration; fix #4382

Fix test in mruby-io

Fix missing assertions in `mruby-random` test

Merge pull request #4379 from shuujii/extract-similar-codes-to-macros-for-math-opcode-in-mrb_vm_exec

Extract similar codes to macros for math opcode in `mrb_vm_exec()`

Fix memory leak for hash table index if occur out of memory

Fix wrong size of instance variable if occur out of memory

Fix leaked function symbols

Include `RFiber` and `RIstruct` as a part of `RVALUE`

Fix hexdigits convertion