bind/java, internal/mobileinit: add dummy import "C"

not harmful, but this consistency may simplify cgo handling
in some custom build systems

Change-Id: Id4692986725b3737c23cdeb9ce1a1fa2bc9f7dad
Reviewed-on: https://go-review.googlesource.com/18615
Reviewed-by: David Crawshaw <crawshaw@golang.org>

bind/java/doc.go

@@ -8,3 +8,5 @@
 //
 // Currently, this works only for android.
 package java
+
+import "C"

internal/mobileinit/mobileinit.go

@@ -7,3 +7,5 @@
 //
 // Long-term, some code in this package should consider moving into Go stdlib.
 package mobileinit
+
+import "C"