Using fputs instead of fprintf

prevents thest compile error messages on gcc 4.8.2 (ubuntu linux)...

objUtil.h: In function ‘objWriter’:
objUtil.h:11:5: error: format not a string literal and no format arguments [-Werror=format-security]
     fprintf(fp, header);
     ^
objUtil.h:12:5: error: format not a string literal and no format arguments [-Werror=format-security]
     fprintf(fp, verts);
     ^
objUtil.h:13:5: error: format not a string literal and no format arguments [-Werror=format-security]
     fprintf(fp, vn);
     ^
objUtil.h:14:5: error: format not a string literal and no format arguments [-Werror=format-security]
     fprintf(fp, vt);
     ^
objUtil.h:15:5: error: format not a string literal and no format arguments [-Werror=format-security]
     fprintf(fp, faces);