no error message for invalid 'pages' value

[xinmingxu]

During verification, there seems no error message printed out for invalid 'pages' value.

I encountered this problem when verifying this BibTeX entry:

@article{Dess07, 
	title = {Storing events to retell them}, 
	volume = {30}, 
	number = {3}, 
	journal = {Behavioral and Brain Sciences}, 
	author = {Dessalles, Jean-Louis}, 
	year = {2007}, 
	pages = {321–322}
	}

btw, the invalid pages value is caused by the dash '–' between page numbers, instead of the common hyphen '-'. Could also add support for the dash family.