Constant arguments can now propogate into function call instances

[JulianKemmerer]

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Final testing ...

[JulianKemmerer]

Broken still :fist:

#include "uintN_t.h"
#pragma MAIN main
uint16_t foo(uint16_t x, uint8_t y)
{
  return x + y;
}
uint16_t bar(uint16_t x, uint8_t y)
{
  return x - y;
}

uint16_t main(uint16_t x, uint8_t y)
{
  return foo(bar(x,y), 1);
}

and different for foo(foo(x,y), 1);