#3851 mos6502 port symbols

[Philipp Klaus Krause]

The mos6502 port now uses some symbols that are neither static, nor contain the port name: at least addSign aopOp, freeAsmop.
All port-specific symbols should be either static (like aopOp in src/z80/gen.c), or be prefixed with the port name (like z80IsReturned in src/z80/gen.c). Otherwise we get problems when linking SDCC (as soon as two ports do what they shouldn't - in this case both the mos6502 port and the pic14 port use these symbols).

P.S.: I'll fix the issue for these three function on the pic14 side. This bug report is about the issue on the mos6502 side.

[Philipp Klaus Krause]

As of [r15449], we should have a working fix on the pic14 side, It is now possible again to build SDCC that supports both pic14 and mos6502 (and this is now the default again). @gorlik: Still, we should also fix the mos6502 side.

[Gabriele Gorla]

I am slowly adding the m6502_ prefix to all external symbols. [r16357]

[Gabriele Gorla]

fixed in [r16536]