Refactor class to represent structure.

We had a TTypeLine to represent a structure field,
which simply encapsulated a TType and line number.
The line number was only used during parsing for error reporting.
There is no need to store a line number because it is already
available in the parser token.

TEST=WebGL conformance tests

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git-svn-id: 736b8ea6-26fd-11df-bfd4-992fa37f6226
10 files changed