Backport I110b653a58f3
All the other property stuff is already here. Property setting was
only in libcutils previously to leverage a utility function / constant
or two.
Unfortunately in the process of fixing a race condition we would've
had to do break abstraction boundaries and put some libc-internal
details into libcutils so instead of that we'll just move this
into bionic.
Along with Iee1ca9b7, this now passes:
$ adb shell am instrument -w -e class android.os.SystemPropertiesTest \
com.android.frameworks.coretests.systemproperties/android.test.InstrumentationTestRunner
Bug: 3511230
Change-Id: I1b588db3344169621e1279ecc0b660cf4e1015d7
Also add missing declarations to misc. functions.
Fix clearerr() implementation (previous was broken).
Handle feature test macros like _POSIX_C_SOURCE properly.
Change-Id: Icdc973a6b9d550a166fc2545f727ea837fe800c4
