JSXTransformer doesn't handle element with "=" as content

[Daniel15]

Expected: All three of the below work:

JSXTransformer.transform('/** @jsx React.DOM*/ <span className="o">=</span>')
JSXTransformer.transform('/** @jsx React.DOM*/ <span className="o">{'='}</span>')
JSXTransformer.transform('/** @jsx React.DOM*/ <span className="o">{"="}</span>')

Actual: Only the last one works. The other two throw different errors:

JSXTransformer.transform('/** @jsx React.DOM*/ <span className="o">=</span>')
Error: Parse Error: Line 1: Unexpected token >=

JSXTransformer.transform('/** @jsx React.DOM*/ <span className="o">{'='}</span>')
ReferenceError: Invalid left-hand side in assignment

JSXTransformer.transform('/** @jsx React.DOM*/ <span className="o">{"="}</span>')
Object {code: "/** @jsx React.DOM*/ React.DOM.span({className: "o"}, "=")", extra: Object, sourceMap: SourceMapGenerator, sourceMapFilename: "source.js"}

[zpao]

Already closed here (#998) and redirected to esprima - https://github.com/facebook/esprima/issues/37, so doing the same again.