adb: Use bionic's strtok_r() for Windows

A recent change use strtok_r which broke the Windows build.
Clear this potential landmine by adding adb_strtok_r to sysdeps.h
in the typical fashion.  For Windows, the actual implementation
in sysdeps_win32.c was copied from bionic/libc/string/strtok.c.

Change-Id: Ibb71555bc429f7058c07c3d39e0b62859c79635c
Signed-off-by: Scott Anderson <saa@android.com>