fastboot: turn on -Werror

- Deal with a missing initializer issue
- Deal with some -Wunused issues
- Deal with some signed/unsigned issues
- switch to usleep from sleep to facilitate win_sdk compile

Change-Id: I64e32a5b0782aeed9582f489e866173c4df1afbf
diff --git a/fastboot/Android.mk b/fastboot/Android.mk
index 05ddf2a..73794a0 100644
--- a/fastboot/Android.mk
+++ b/fastboot/Android.mk
@@ -21,7 +21,7 @@
 LOCAL_SRC_FILES := protocol.c engine.c bootimg.c fastboot.c util.c fs.c
 LOCAL_MODULE := fastboot
 LOCAL_MODULE_TAGS := debug
-LOCAL_CFLAGS += -std=gnu99
+LOCAL_CFLAGS += -std=gnu99 -Werror
 
 ifeq ($(HOST_OS),linux)
   LOCAL_SRC_FILES += usb_linux.c util_linux.c
@@ -72,6 +72,7 @@
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := usbtest.c usb_linux.c util.c
 LOCAL_MODULE := usbtest
+LOCAL_CFLAGS := -Werror
 include $(BUILD_HOST_EXECUTABLE)
 endif