Created attachment 179906 [details] [review]
valaparser: support for Python-like slice syntax

The vala slice syntax is similar to python, but it doesn't allow to use defaults start/stop values like python (i.e.: array[start:], or array[:stop]).

This patch fixes it, allowing to use slicing functions like:
	string word = "Hello World";
	print(word[:2]+"\n");
	// alias for:
	print(word[0:2]+"\n");

	print(word[2:]+"\n");
	// alias for:
	print(word[2:0]+"\n"); // 0 stands for word.length, see #639586

For strings support it needs the patch which fixes the Bug 639586
For arrays complete support it needs the patch which fixes the Bug 641267