Fix "instance variable @options not initialized" warning in verbose mode

[kolen]

When running in verbose mode (-w or --verbose or $VERBOSE = true), when instantiating any renderer (subclass of Redcarpet::Render::Base) without parameters, warning is shown about @options not initialized:

warning: instance variable @options not initialized

(For example, it can be seen if running RUBYOPT=-w rake test)

It's caused by accessing @options with rb_iv_get:

redcarpet/ext/redcarpet/rc_render.c

Lines 414 to 415 in 1c71f5e

	if (rb_iv_get(self, "@options") == Qnil)
	rb_iv_set(self, "@options", rb_hash_new());

Replaced it with rb_attr_get, according to source, it's the same as rb_ivar_get but without warnings and without conversion of undef to nil, not sure if it's the right method by design (seems that it is).

Also not sure what is purpose for @options in render objects: there are no reads of it and all options are passed to actual renderer in constructor only, overwriting @options later is meaningless. Redcarpet::Markdown object adds its options to it when initialized but I can't figure out where these options are used (and these options are not for renderer but for "extensions"). Update: it's feature #560 and intended for custom renderers to be able to access "extension options" and not only renderer options passed in constructor.

I can try to detect warnings in tests, but I'm not sure if it's right idea (it can only be done in quirky ways such as capturing stderr), so not changed tests for now.

[fedotov2d]

Looks good! 👍

[robin850]

Thank you very much @kolen ! :-)