buildDecl was visiting all decls in source order, but the spec
calls for visiting all vars and init() funcs in order, then
all remaining functions. These two passes are now called
buildInit(), buildFuncDecl().
+ Test.
Also:
- Added workaround to gcimporter for Func with pkg==nil.
- Prog.concreteMethods has been merged into Pkg.values.
- Prog.concreteMethod() renamed declaredFunc().
- s/mfunc/obj/ (name cleanup from recent gri CL)
R=gri
CC=golang-dev
https://golang.org/cl/12030044
