Paul, When I compile code for my teensy3 I get a warning in usb_serial.c. This isn't a new warning but persists even in the latest 1.14 rc3 version. I think it's a simple case that you need to add an include of string.h in that file. The compile statement and warning is:
C:\arduino\arduino-1.0.5\hardware\tools\arm-none-eabi\bin\arm-none-eabi-gcc -c -g -Os -Wall -ffunction-sections -fdata-sections -mcpu=cortex-m4 -DF_CPU=48000000 -MMD -DUSB_VID=null -DUSB_PID=null -DARDUINO=105 -mthumb -nostdlib -D__MK20DX128__ -DTIME_T=1369576988 -DUSB_SERIAL -DLAYOUT_US_ENGLISH -IC:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3 C:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3\usb_serial.c -o C:\froeber\Projects\Kuji_lighter\SmartLighter\Arduino\Build\usb_serial.c.o
C:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3\usb_serial.c: In function 'usb_serial_read':
C:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3\usb_serial.c:81:3: warning: implicit declaration of function 'memcpy' [-Wimplicit-function-declaration]
C:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3\usb_serial.c:81:3: warning: incompatible implicit declaration of built-in function 'memcpy' [enabled by default]
C:\arduino\arduino-1.0.5\hardware\tools\arm-none-eabi\bin\arm-none-eabi-gcc -c -g -Os -Wall -ffunction-sections -fdata-sections -mcpu=cortex-m4 -DF_CPU=48000000 -MMD -DUSB_VID=null -DUSB_PID=null -DARDUINO=105 -mthumb -nostdlib -D__MK20DX128__ -DTIME_T=1369576988 -DUSB_SERIAL -DLAYOUT_US_ENGLISH -IC:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3 C:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3\usb_serial.c -o C:\froeber\Projects\Kuji_lighter\SmartLighter\Arduino\Build\usb_serial.c.o
C:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3\usb_serial.c: In function 'usb_serial_read':
C:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3\usb_serial.c:81:3: warning: implicit declaration of function 'memcpy' [-Wimplicit-function-declaration]
C:\arduino\arduino-1.0.5\hardware\teensy\cores\teensy3\usb_serial.c:81:3: warning: incompatible implicit declaration of built-in function 'memcpy' [enabled by default]