## Checks for header files.
AC_MSG_NOTICE([CHECKS for header files])
#
+# Define NO_SYS_SELECT_H if you don't have sys/select.h.
+AC_CHECK_HEADER([sys/select.h],
+[NO_SYS_SELECT_H=],
+[NO_SYS_SELECT_H=UnfortunatelyYes])
+AC_SUBST(NO_SYS_SELECT_H)
+#
# Define OLD_ICONV if your library has an old iconv(), where the second
# (input buffer pointer) parameter is declared with type (const char **).
AC_DEFUN([OLDICONVTEST_SRC], [[
[NO_SETENV=YesPlease])
AC_SUBST(NO_SETENV)
#
+# Define NO_UNSETENV if you don't have unsetenv in the C library.
+AC_CHECK_FUNC(unsetenv,
+[NO_UNSETENV=],
+[NO_UNSETENV=YesPlease])
+AC_SUBST(NO_UNSETENV)
+#
# Define NO_MKDTEMP if you don't have mkdtemp in the C library.
AC_CHECK_FUNC(mkdtemp,
[NO_MKDTEMP=],