Dependencies: Use ArduinoSTL instead of custom StandardCplusplus fork

After updating the AVR platform SDK to the most recent version, the very old StandardCplusplus fork tripped. It looks like Mika Matera is maintaining the canonical ArduinoSTL well, so let's use it without further ado.

Author: amotl

backdoor/multihop/multihop.ino

@@ -126,9 +126,7 @@ The firmware serves different purposes, you can configure it as a »sensor node
  #include <Arduino.h>
 
  // Standard C++ for Arduino
- #include <new.cpp>
- #include <StandardCplusplus.h>
- #include <func_exception.cpp>
+ #include <ArduinoSTL.h>
  #include <MemoryFree.h>
 
 #endif

backdoor/multihop/platformio.ini

@@ -18,7 +18,7 @@ framework = arduino
 lib_deps =
  apechinsky/MemoryFree@^0.3
  mikem/RadioHead@^1.120
- https://github.com/hiveeyes/StandardCplusplus#next
+ mike-matera/ArduinoSTL@^1
  ../../libraries/Terrine
 build_flags =
  -fdiagnostics-color
@@ -54,6 +54,7 @@ board = pro8MHzatmega328
 lib_deps =
  ${env.lib_deps}
  ${node-common.lib_deps}
+ lowpowerlab/SPIFlash@^101
  lowpowerlab/RFM69@^1.5
 build_flags =
  ${env.build_flags}