[avr-gcc-list] Bug when -mcall-prologues is used in C++

[An . Kaiser]

When using -mcall-prologues in C++, the label embedded in the prologue
sequence is output as a typed C++ name. Needless to say that the
assembler fails.

/* prologue: frame size=4 */
        ldi r26,lo8(4)
        ldi r27,hi8(4)
        ldi r30,pm_lo8(.L_int f()_body)
        ldi r31,pm_hi8(.L_int f()_body)
        rjmp __prologue_saves__+32
.L_int f()_body:
/* prologue end (size=5) */