liblog: replace "frontend" with "transport"

We still do not have any users of the 'frontend' interface, let's
right a wrong and rename it to 'transport' as it makes more sense.
Renames android_log_set_frontend, android_log_get_frontend and
include/log/log_frontend.h.

SideEffects: None
Test: gTest liblog-unit-tests
Bug: 27405083
Change-Id: I7c1c0f3dfdc7cf047285403e306edbd16ad1324d
13 files changed
tree: d281226a039f65308b5442ed12ae2269d30fc043
  1. liblog/
  2. logcat/
  3. logd/
  4. logwrapper/