Make c++11 requirement dependent upon pckg-config.

Author: evoskuil

configure.ac

@@ -45,9 +45,6 @@ AC_PROG_LIBTOOL
 # Compute the canonical host-system type variable host, including host_os.
 AC_CANONICAL_HOST
 
-# Check for baseline language coverage in the compiler for the C++11 standard.
-AX_CXX_COMPILE_STDCXX_11([noext], [mandatory])
-
 # Enable silent rules option.
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])