[ADOL-C] Compiler warnings

[Brad Bell]

Using clang++ 6.0.1, and the current trunk for
    https://projects.coin-or.org/svn/ADOL-C
I am getting a lot of conversion warnings in the ADOL-C source.
For example:

adolc/include/adolc/advector.h:132:128: warning: implicit conversion loses integer precision: 
'size_t' (aka 'unsigned long') to 'locint' (aka 'unsigned int') [-Wshorten-64-to-32]
     ADOLC_DLL_EXPORT advector(const advector& x) : blk(x.size()), data(x.size()) { 
adolc_vec_copy(data.data(),x.data.data(),x.size()); }

adolc/include/adolc/adouble.h:376:9: warning: implicit conversion turns floating-point number into 
integer: 'double' to 'bool' [-Wfloat-conversion]
     if (coval)

adolc/include/adolc/adalloc.h:71:23: warning: implicit conversion changes signedness: 'int' to 
'size_t' (aka 'unsigned long') [-Wsign-conversion]
     return myalloc2(m,n);

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