test($compile): style attr should be interpolated when replace is true
fix($compile): interpolation in style attributes when replace is true

Fix the interpolation of style attributes in directive templates when
the directive sets replace: true.

In templateMergeAttributes(), copy the value of the style attributes
to the dst object for use in the attr interpolation directive's link
function, separating the element's style value and any src object
style value with semicolons.

The previous behavior, from the "Compiler v2.0" commit, doesn't copy
the style attribute to dst in templateMergeAttributes(). Instead, it
just appends the element's style attr value to itself.

Since the attrs object provided to the attr interpolation directive will
not have a 'style' property, $interpolate() will be passed an undefined
value as its 'text' argument, leading to an exception when $interpolate
dereferences the length property of the undefined variable.

templateMergeAttributes() is only called when directive.replace is true,
so this bug only occurs when:

1) A directive sets replace: true
2) The directive's template's top level element attempts to interpolate
   a value into an attribute named 'style.'