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;
^
^

IEC 61131-3
===========

    IEC-61131 is a normative document provided by the standards organization IEC
    (International Electrotechnical Commission) and describing a standard for
    implementing programmable controllers.


    The part 3 of this document (commonly named IEC 61131-3) specifies syntax and 
    semantics for programming language for programmable controllers. Beremiz
    implements all the languages described in this document. 


    http://www.iec.eu
        
PLCopen TC6
===========
   
    PLCopen is a vendor- and product-independent worldwide association defining
    international standards for various topics related to control programming.
    For this purpose, PLCopen has 6 technical committees.
   
   
    The goal of the sixth committee (TC6) is to define a standard file format, 
    based on XML, for exchanging programmables controllers programmed using 
    IEC 61131-3 languages. Beremiz uses this file format for saving the PLC
    programs of projects.
   
   
    http://www.plcopen.org