Bug 1083913: Replace TokenBuf::base and TokenStream::rawBase with better abstractions. r=shu
Bug 1083913: Make js::TokenStream::TokenBuf store the starting offset of its buffer explicitly, not implicitly as a bias on base_. r=shu
Bug 1083913: Make TokenStream::linebase an offset, not a pointer into nothingness. r=shu
Bug 1083913: Add a no-op js::frontend::Parser::checkOptions() method, and ensure that it's called everywhere. r=shu
Bug 1083913: Add a 'columnNumber' parameter to the JS shell's 'evaluate' and 'offThreadCompileScript' functions. r=shu
Bug 1083913: Column spans are restricted to 31-bit, not 24-bit, signed values. r=shu

This also cleans up the column span / offset conversions, and fixes some comments.
Bug 1083913: Restrict source lines included in error messages to the source text actually available. r=shu