non-const ptr to const char* literal

[~/src] cat test.cpp
int main()
{
        char* a = "hello";
        return 0;
}
[~/src] g++ --version
g++ (GCC) 4.4.7 20120313 (Red Hat 4.4.7-3)
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[~/src] g++ -o test.exe test.cpp
test.cpp: In function ‘int main()’:
test.cpp:3: warning: deprecated conversion from string constant to ‘char*’
[~/src] g++ -Wall -o test.exe test.cpp
test.cpp: In function ‘int main()’:
test.cpp:3: warning: deprecated conversion from string constant to ‘char*’
test.cpp:3: warning: unused variable ‘a’
[~/src] vanilla-g++-4.7.2 -o test.exe test.cpp
test.cpp: In function ‘int main()’:
test.cpp:3:12: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]
[~/src] vanilla-g++-4.7.2 -Wall -o test.exe test.cpp
test.cpp: In function ‘int main()’:
test.cpp:3:12: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]
test.cpp:3:8: warning: unused variable ‘a’ [-Wunused-variable]