update doc.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39750 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Refactor rb_file_expand_path_internal for dir_string corner cases

* win32/file.c (get_user_from_path):  add internal function that retrieves
  username from supplied path (refactored).
* win32/file.c (rb_file_expand_path_internal):  refactor expansion of user
  home to use get_user_from_path and cover dir_string corner cases.
  [ruby-core:53168] [Bug #8034]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39751 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* file.c (rb_sys_fail_path0): add to append the name of called function
  to ease debugging for example blow umask_spec failure.
  http://fbsd.rubyci.org/~chkbuild/ruby-trunk/log/20130309T010202Z.diff.html.gz

* file.c (rb_sys_fail_path): use rb_sys_fail_path0.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39752 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* file.c (rb_sys_fail_path): use rb_sys_fail_path0 only on GCC.
  __func__ is C99 feature.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39753 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
configure.in, file.c: RUBY_FUNCTION_NAME_STRING

* configure.in (rb_cv_function_name_string): macro for function name
  string predefined identifier, __func__ in C99, or __FUNCTION__ in
  gcc.
* file.c (rb_sys_fail_path): use RUBY_FUNCTION_NAME_STRING.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39754 b2dd03c8-39d4-4d8f-98ff-823fe69b080e