Avoid 'possible loss of data' casting in binary search

Fix "Use `MRB_SYM()` for error class retrieval"; ref 2ddfd50d

Because it may not be expected result.
example: https://wandbox.org/permlink/F5Mp7IEJ1VY3CFLp

The new macro (`MRB_E_SYM`) was not being used, so it is being used. Also
`MRB_E_SYM` is confusing with `MRB_SYM_E`, so change it to `MRB_ERROR_SYM`.

This reverts commit 34f82f24.
Ref #5282

To describe how to use symbols, especially preallocated symbols from C.

Or no argument at all.

Where `mruby-config` command should be generated.

Note that `MRB_SYM()` is only available when `mruby/presym.h` is
included. Use `mrb_intern_lit()` otherwise.

This reverts commit dc51d89a.

Fix TYPO and checking minor version in RITE BINARY HEADER

For easier compiling and linking of the application embedding `mruby`

As CRuby does.

ref dc51d89a

Fix typo

Instead of including `mruby/presym.h` everywhere, we provided the
fallback `mruby/presym.inc` under `include/mruby` directory, and specify
`-I<build-dir>/include` before `-I<top-dir>/include` in `presym.rake`.
So even when someone drops `-I<build-dir>/include` in compiler options,
it just compiles without failure.

From 48 bytes to 40 bytes on 64 bit platforms (unchanged on 32 bit).

Merge branch 'avoid-including-presym.inc-in-existing-header-files' of https://github.com/shuujii/mruby into shuujii-avoid-including-presym.inc-in-existing-header-files

`calc_crc_16_ccitt()` consumes a lot of clock cycles in programs like
`mrbtest` which loads a lot of dumped binary. Error detection for flaky
channels should be done in the higher level.

Note: `mruby/c` should be updated to support this change.

Fix that Hash may not contain any empty buckets

The Hash implementation assumed that there were always empty buckets, but
sometimes there were only active or deleted buckets (no empty buckets).
Therefore, fix it so that this situation does not occur.

### Example

```ruby
# example.rb
class A
  attr_reader :v
  def initialize(v) @v = v end
  def ==(o) @v == o.v end
  def hash; @v end
  def to_s; "#{self.class}[#{@v}]" end
  alias eql? ==
  alias inspect to_s
end

keys = (0..31).map{A.new(_1)}
h = {}
(0..16).each{h[keys[_1]] = _1}
(17..31).each do
  k = keys[_1]
  h[k] = _1
  h.delete(k)
end
p h.keys
```

#### Before this patch:

```console
$ bin/mruby example.rb
[A[0], A[1], A[2], A[3], A[4], A[5], A[6], A[7], A[8], A[9], A[10], A[11], A[12], A[13], A[14], A[15], A[16], A[30], A[31]]
```

#### After this patch:

```console
$ bin/mruby example.rb
[A[0], A[1], A[2], A[3], A[4], A[5], A[6], A[7], A[8], A[9], A[10], A[11], A[12], A[13], A[14], A[15], A[16]]
```