Remove newlib dependency, include own stdio/string/assert

firmware/apps/dfu/Makefile

@@ -1 +1,12 @@
+
 C_FILES += $(C_LIBUSB_DFU)
+
+# Trace level used for compilation
+# (can be overriden by adding TRACE_LEVEL=#number to the command-line)
+# TRACE_LEVEL_DEBUG      5
+# TRACE_LEVEL_INFO       4
+# TRACE_LEVEL_WARNING    3
+# TRACE_LEVEL_ERROR      2
+# TRACE_LEVEL_FATAL      1
+# TRACE_LEVEL_NO_TRACE   0
+TRACE_LEVEL ?= 3