swift234

fix <rdar://problem/24251022> Swift 2: Bad Diagnostic Message When Adding Different Integer Types

Previously we would produce:

t.swift:3:3: error: binary operator '+=' cannot be applied to operands of type 'Int' and '_'
a += a + b
~ ^  ~~~~~

with a candidate set to follow.  Now we properly match up the inout/lvalue type and produce
the following more specific diagnostic:

t.swift:3:10: error: cannot convert value of type 'UInt32' to expected argument type 'Int'
a += a + b
         ^

pointing the the "b".