drfront_bufprint call from C++ leads to warning

Created by: mxmssh

I'm calling drfront_bufprint interface from drltrace frontend and have the following warnings:

drltrace_frontend.cpp: In function ‘void configure_application(char*, char**, void**, const char*, const char*, const char*)’: drltrace_frontend.cpp:71:87: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]

We have to change char *fmt to const char *fmt.