fix many compilation warnings about static variables used by non-static functions

[CC] plc_main.c -> plc_main.o
/tmp/be/build/plc_main.c:396:40: warning: ‘LogBuff’ is static but used in inline function ‘copy_from_log’ which is not static
memcpy((char*)buf + remaining, LogBuff[level], size - remaining);
^
/tmp/be/build/plc_main.c:395:22: warning: ‘LogBuff’ is static but used in inline function ‘copy_from_log’ which is not static
memcpy(buf, &LogBuff[level][buffpos], remaining);
^
...

^
/tmp/be/build/plc_debugger.c:825:20: warning: ‘retain_offset’ is static but used in inline function ‘BufferIterator’ which is not static
Retain(retain_offset, size, real_value_p);
^
/tmp/be/build/plc_debugger.c:823:47: warning: ‘retain_offset’ is static but used in inline function ‘BufferIterator’ which is not static
unsigned int next_retain_offset = retain_offset + size;
^
^