Remove use of unicode superscripts in configure --help

Author: Matthias Koeppe

m4/sage_spkg_configure.m4

@@ -63,7 +63,7 @@ echo "Checking whether SageMath should install SPKG $1..." >& AS_MESSAGE_FD
 AS_BOX([Checking whether SageMath should install SPKG $1...]) >& AS_MESSAGE_LOG_FD
 
 AC_ARG_WITH([system-]SPKG_NAME,
-       AS_HELP_STRING(--with-system-SPKG_NAME={no|yes⁽ᵈᵉᶠᵃᵘˡᵗ⁾|force (error if no usable version is found)},
+       AS_HELP_STRING(--with-system-SPKG_NAME={no|yes (default)|force (exit with an error if no usable version is found)},
            [detect and use an existing system SPKG_NAME]),
        [AS_VAR_SET(SPKG_USE_SYSTEM, [$withval])],
        [AS_VAR_SET(SPKG_USE_SYSTEM, [yes])]

m4/sage_spkg_enable.m4

@@ -12,7 +12,7 @@ AC_DEFUN([SAGE_SPKG_ENABLE], [dnl
   ], [dnl
     dnl optional/experimental packages
     AC_ARG_ENABLE(SPKG_NAME,
-      AS_HELP_STRING([--enable-]SPKG_NAME={no|if_installed⁽ᵈᵉᶠᵃᵘˡᵗ⁾|yes},
+      AS_HELP_STRING([--enable-]SPKG_NAME={no|if_installed (default)|yes},
                      [enable build and use of the SPKG_TYPE package $3], [26], [100])
 AS_HELP_STRING([], [* package info: ./sage -info SPKG_NAME])
 AS_HELP_STRING([--disable-]SPKG_NAME,