Add encoding argument to `Integral#chr`

Currently, `Integral#chr` in mruby changes behavior by `MRB_UTF8_STRING`
setting.

before this patch:

  $ bin/mruby -e 'p 171.chr'  #=> "\xab"  (`MRB_UTF8_STRING` is disabled)
  $ bin/mruby -e 'p 171.chr'  #=> "«"     (`MRB_UTF8_STRING` is enabled)

This behavior is incompatible with Ruby, and a little inconvenient because
it can't be interpreted as ASCII-8BIT with `MRB_UTF8_STRING`, I think.

So add encoding argument according to Ruby.

after this patch:

  $ bin/mruby -e 'p 171.chr'                #=> "\xab"
  $ bin/mruby -e 'p 171.chr("ASCII-8BIT")'  #=> "\xab"
  $ bin/mruby -e 'p 171.chr("UTF-8")'       #=> "«"

Allow only `String` for encoding because mruby doesn't have `Encoding`
class, and `"ASCII-8BIT"` (`"BINARY"`) and `"UTF-8"` (only with
`MRB_UTF8_STRING`) are valid value (default is `"ASCII-8BIT"`).

1 files changed, 1 insertions, 1 deletions

diff --git a/mrbgems/mruby-string-ext/mrblib/string.rb b/mrbgems/mruby-string-ext/mrblib/string.rb
index fdaf2f960..e57d75355 100644
--- a/mrbgems/mruby-string-ext/mrblib/string.rb
+++ b/mrbgems/mruby-string-ext/mrblib/string.rb
@@ -414,7 +414,7 @@ class String
       e = max.ord
       while c <= e
         break if exclusive and c == e
-        yield c.chr
+        yield c.chr(__ENCODING__)
         c += 1
       end
       return self