Remove redundant declarations from M100 code

Marlin/M100_Free_Mem_Chk.cpp

@@ -47,21 +47,6 @@ extern void* __brkval;
 extern size_t  __heap_start, __heap_end, __flp;
 
 
-//
-// Declare all the functions we need from Marlin_Main.cpp to do the work!
-//
-
-int code_value_int();
-bool code_seen(char);
-void serial_echopair_P(const char*, float);
-void serial_echopair_P(const char*, double);
-void serial_echopair_P(const char*, unsigned long);
-void serial_echopair_P(const char*, int);
-void serial_echopair_P(const char*, long);
-
-
-
-
 //
 // Utility functions used by M100 to get its work done.
 //
@@ -175,8 +160,7 @@ void gcode_M100() {
   //
 #if ENABLED(M100_FREE_MEMORY_CORRUPTOR)
   if (code_seen('C')) {
-    int x;      // x gets the # of locations to corrupt within the memory pool
-    x = code_value_int();
+    int x = code_value_int(); // x gets the # of locations to corrupt within the memory pool
     SERIAL_ECHOLNPGM("Corrupting free memory block.\n");
     ptr = (unsigned char*) __brkval;
     SERIAL_ECHOPAIR("\n__brkval : ", ptr);