Fix a shell-command typo in the fallback from GMP to LibTomMath.  Patch both
the Autoconf input and the generated configure script so the correction
survives a future autoreconf.

--- a/configure.ac
+++ b/configure.ac
@@ -171 +171 @@ AS_CASE(["$with_bignum"],
-     AS_IF([text x"$with_bignum" = xyes || test x"$with_bignum" = xtommath],
+     AS_IF([test x"$with_bignum" = xyes || test x"$with_bignum" = xtommath],
--- a/configure
+++ b/configure
@@ -24846,7 +24846,7 @@ fi
 fi

 fi
-     if text x"$with_bignum" = xyes || test x"$with_bignum" = xtommath; then :
+     if test x"$with_bignum" = xyes || test x"$with_bignum" = xtommath; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for mp_init in -ltommath" >&5
 $as_echo_n "checking for mp_init in -ltommath... " >&6; }
 if ${ac_cv_lib_tommath_mp_init+:} false; then :