Various warnings in flute

[robtaylor]

../../flute/src/3.1/flute.cpp:1474:27: warning: format specifies type 'int' but the argument has type 'int64_t' (aka 'long long') [-Wformat]
        printf("%d %d\n", t.branch[i].x, t.branch[i].y);
                ~~        ^~~~~~~~~~~~~
                %lld
../../flute/src/3.1/flute.cpp:1474:42: warning: format specifies type 'int' but the argument has type 'int64_t' (aka 'long long') [-Wformat]
        printf("%d %d\n", t.branch[i].x, t.branch[i].y);
                   ~~                    ^~~~~~~~~~~~~
                   %lld
../../flute/src/3.1/flute.cpp:1475:29: warning: format specifies type 'int' but the argument has type 'int64_t' (aka 'long long') [-Wformat]
        printf("%d %d\n\n", t.branch[t.branch[i].n].x,
                ~~          ^~~~~~~~~~~~~~~~~~~~~~~~~
                %lld
../../flute/src/3.1/flute.cpp:1476:16: warning: format specifies type 'int' but the argument has type 'int64_t' (aka 'long long') [-Wformat]
               t.branch[t.branch[i].n].y);
               ^~~~~~~~~~~~~~~~~~~~~~~~~
4 warnings generated.
[797/1078] Compiling C++ object flute/src/3.1/libflute.dylib.p/heap.cpp.o
../../flute/src/3.1/heap.cpp:28:17: warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
      err_exit( "Cannot reallocate memory in allocate_heap!" );
                ^
1 warning generated.
[798/1078] Compiling C++ object flute/src/3.1/libflute.dylib.p/neighbors.cpp.o
../../flute/src/3.1/neighbors.cpp:44:17: warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
      err_exit( "Cannot allocate memory in allocate_nn_arrays!" );
                ^