build: use -pedantic-errors flag in autotools

configure.ac

@@ -18,8 +18,8 @@ AC_SUBST(OPENDHT_PATCH_VERSION, opendht_patch_version)
 
 AC_ARG_ENABLE([debug], AS_HELP_STRING([--enable-debug], [Build in debug mode, adds stricter warnings, disables optimization]))
 AS_IF([test "x$enable_debug" = "xyes"],
-      [CXXFLAGS="${CXXFLAGS} -g -Wno-return-type -Wall -Wextra -Wnon-virtual-dtor -O0"],
-      [CXXFLAGS="${CXXFLAGS} -O3"])
+      [CXXFLAGS="${CXXFLAGS} -g -Wno-return-type -Wall -Wextra -Wnon-virtual-dtor -O0 -pedantic-errors"],
+      [CXXFLAGS="${CXXFLAGS} -O3 -pedantic-errors"])
 
 AC_PROG_CXX
 AM_PROG_AR