Fix FTBFS problem with GCC-6

Fix FTBFS problem with GCC-6

GCC-6 is pickier about some of the type conversions causing the Fedora
24 mass rebuild the build of oprofile failed with:

make[3]: Entering directory '/builddir/build/BUILD/oprofile-1.1.0/libutil++'
g++ -DHAVE_CONFIG_H -I. -I..  -I ../libutil -I ../libop -I ../libpp   -W -Wall -fno-common -ftemplate-depth-50 -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m32 -march=i686 -mtune=atom -fasynchronous-unwind-tables -c -o op_bfd.o op_bfd.cpp
op_bfd.cpp: In member function 'void op_bfd::get_symbol_range(symbol_index_t, long long unsigned int&, long long unsigned int&) const':
op_bfd.cpp:538:47: error: cannot convert 'std::ostream {aka std::basic_ostream<char>}' to 'const bool' in initialization
  bool const verbose = cverb << (vbfd & vlevel1);
                                               ^
op_bfd.cpp:546:7: error: in argument to unary !
  if (!verbose)
       ^~~~~~~

Avoid the intermediate bool type to make GCC-6 happy.

Change-Id: I84a535ffa30ea7c3b46682309d3881ca016910b4
Signed-off-by: William Cohen <wcohen@redhat.com>