Partially revert f2212e33. Make some constructors public again.
There is some code in the Android SDK using reflection to find the constructor
of one of our custom views. As such, a previous change in f2212e33 broke this
code because it made constructors package local. This partially reverts the bit
of f2212e33 which pertains to the constructors accessed using reflection.
Fixes#519.
See merge request !187
c2c8c55862