PR go/65755
compiler, runtime, reflect: Use reflection string for type comparisons.

Change the runtime and reflect libraries to always use only
the type reflection string to determine whether two types are
equal.  It previously used the PkgPath and Name values for a
type name, but that required a PkgPath that did not match the
gc compiler.

Change the compiler to use the same PkgPath value as the gc
compiler in all cases.

Change the compiler to put the receiver type in the reflection
string for a type defined inside a method.

From-SVN: r222194