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;
^
^

from ..toolchain_gcc import toolchain_gcc

class Linux_target(toolchain_gcc):
    dlopen_prefix = "./"
    extension = ".so"
    def getBuilderCFLAGS(self):
        return toolchain_gcc.getBuilderCFLAGS(self) + ["-fPIC"]
    def getBuilderLDFLAGS(self):
        return toolchain_gcc.getBuilderLDFLAGS(self) + ["-shared", "-lrt"]