Compile warnings

[LeventErkok]

Low hanging fruit. This is on Mac; but I suppose it applies to all platforms.

../src/smt/theory_arith_pp.h:524:9: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
        sprintf(buffer, "arith_%d.smt", id);

../src/ast/proofs/proof_checker.cpp:1252:5: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
    sprintf(buffer, "proof_lemma_%d.smt2", m_proof_lemma_id);

../src/ast/format.cpp:153:9: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
        SPRINTF_D(buffer, i);
        ^

../src/ast/format.cpp:159:9: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
        SPRINTF_U(buffer, u);

../src/util/debug.cpp:104:13: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
            sprintf(buffer, "gdb -nw /proc/%d/exe %d", getpid(), getpid());