Because a structure that is an element of `presym_table` has padding, split
it into individual arrays for name and length.

#### Result (64-bit CPU with full-core gembox)

|        |   mruby    | libmruby.a |
|--------|------------|------------|
| Before | 1,087,444B | 1,476,872B |
| After  | 1,079,340B | 1,469,784B |

Rename `.i` created for presym scan to `.pi`

This is because compiler's `-save-temps=obj` option creates `.i` with the
same name.

Fix typos in `mruby/presym/{disable,enable}.h` [ci skip]

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