+###
+# AC_PROG_CPP_WERROR
+# Used for autoconf 2.5x to force AC_PREPROC_IFELSE to reject code which
+# triggers warnings from the preprocessor. Will be in autoconf 2.58.
+# For now, using this also overrides header checks to use only the
+# preprocessor (matches 2.13 behavior; matching 2.58's behavior is a
+# bit harder from here).
+# Eventually autoconf will default to checking headers with the compiler
+# instead, and we'll have to do this differently.
+
+# AC_PROG_CPP_WERROR
+