* encoding.c (rb_enc_code_to_mbclen): add new function which returns
mbclen from codepoint like as rb_enc_codelen() but 0 for invalid
char.
* include/ruby/encoding.h (rb_enc_code_to_mbclen): declaration and
shortcut macro.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42077 b2dd03c8-39d4-4d8f-98ff-823fe69b080e