Remove unused Rake rules

Revert "Create presym files for each build target" (58ba883e)

Due to the above changes, it may not work with the existing build
configurations in cross-compilation (even if we can build without presym),
therefore revert it once (ref https://github.com/mruby/mruby/pull/5202#issuecomment-735412643). Sorry for the lack of consideration.

Improves dump irep

Fixed print catch handler address in codedump; ref #5200

Alleviates confusingness.

ref #5203

It became 32 bits in #5200, but only the upper 16 bits were printed.

Use `MRB_SYM` in `src/gc.c`

Fix heap buffer overflow when dump irep

Currently, the size of writing in heap by write_irep_record() is
bigger than The size that is calculated by get_irep_record_size.

Therefore, irep is dumped over the size of allocating memory when we
execute dump_irep().

Change the catch handler address to 32 bits

Follow commit 7150c675 .

Currently, the source file language in the core is C only, and C++,
Objective-C, and Assembly are not used, so Rake rules for them are removed.

Fix incorrect regexp creation in `tasks/presym.rake`

Fix build failure; ref #5194

Fix the following two issues:

1. Compile failure when external gem is specified.
   * https://github.com/mruby/mruby/pull/5194#issuecomment-734303442
2. When there are multiple build targets, presym parsing sometimes fails or
   output result of presym is broken.
   * https://github.com/mruby/mruby/pull/5194#issuecomment-734322142

The root cause of 2 is unknown, but it seems to occur when presym parsing is
performed in parallel, therefore I change them so that they are not run in
parallel.

Add `tools/*` to target directory for presym parsing

Create presym files for each build target

Previously, presym files were always created in `build/{presym,presym.inc}`.
However, this constraint is inconvenient because it is common to use
multiple build configurations and build targets in a single mruby tree.
Therefore, change to create presym file for each build target.

Fix loop condition in `mrb_sym_all_symbols`

Jump target address is `operand (16bit)` + `address of next instruction`.

In addition, `ilen` was made `uint32_t` so that `iseq` length limitation
of 65536 is removed. Only jump target address should be within signed
16bit (-32768 .. 32767).