Remove extern specifiers from function prototype declarations

The extern specifier is redundant for function prototype
declarations; this change is to check if removing the extern specifier
will fix some of code search's issues with code exploration.

Test: m
Merged-In: I7a01bd9911067db9870648bb9192a21bfd74757c
Change-Id: I47f3d4684296428cc72ce40d364876dccbbfd36a