Allow to mixed and specify `*.rb` and `*.mrb` in `bin/mruby`

It is not decides by the extension.
In order to be recognized as a `.mrb` file, the following three points must be satisfied:
- File starts with "RITE"
- At least `sizeof(struct rite_binary_header)` bytes can be read
- `NUL` is included in the first 64 bytes of the file
If these are not met, it is judged as a text file and it is processed as a Ruby script.

The `bin/mruby -b` switch is still available which treats the given file as a `.mrb` file.

New `MRB_API` function:
- `include/mruby/compile.h` and `mrbgems/mruby-compiler/core/parse.y`
  - `mrb_load_detect_file_cxt()` (remove with `MRB_DISABLE_STDIO`)

NOTE:
- Even script files now always open in binary mode for `bin/mruby`.
  The `\r\n` is handled by the `nextc()` function already, so there is no problem even on Windows.
- The `nextc0()` function in `mrbgems/mruby-compiler/core/parse.y` can now specify a string buffer and a file pointer at the same time.
  In this case, get it from the string buffer first.

This patch includes modifies by comment of https://github.com/mruby/mruby/pull/5157.

1 files changed, 1 insertions, 1 deletions

diff --git a/mrbgems/mruby-bin-strip/bintest/mruby-strip.rb b/mrbgems/mruby-bin-strip/bintest/mruby-strip.rb
index 2db3c10b1..5330510a1 100644
--- a/mrbgems/mruby-bin-strip/bintest/mruby-strip.rb
+++ b/mrbgems/mruby-bin-strip/bintest/mruby-strip.rb
@@ -32,7 +32,7 @@ assert('success') do
   o = `#{cmd('mruby-strip')} #{compiled1.path}`
   assert_equal 0, $?.exitstatus
   assert_equal "", o
-  assert_equal `#{cmd('mruby')} #{script_file.path}`, `#{cmd('mruby')} -b #{compiled1.path}`
+  assert_equal `#{cmd('mruby')} #{script_file.path}`, `#{cmd('mruby')} #{compiled1.path}`
 
   o = `#{cmd('mruby-strip')} #{compiled1.path} #{compiled2.path}`
   assert_equal 0, $?.exitstatus