Bug 1325632 - part 2 - don't warn about c++98/c++11 compatibility problems; r=ted.mielczarek

We're going to compile with C++14 and we don't plan to go back.

build/moz.configure/warnings.configure

@@ -57,7 +57,6 @@ check_and_add_gcc_warning('-Wclass-varargs')
 check_and_add_gcc_warning('-Wloop-analysis')
 
 # catches C++ version forward-compat issues
-check_and_add_gcc_warning('-Wc++11-compat-pedantic', cxx_compiler)
 check_and_add_gcc_warning('-Wc++14-compat', cxx_compiler)
 check_and_add_gcc_warning('-Wc++14-compat-pedantic', cxx_compiler)
 check_and_add_gcc_warning('-Wc++1z-compat', cxx_compiler)