[PATCH] Fix SIGIO configure help text

[Dan Nicholson]

Two problems fixed with the configure help text for SIGIO:

1. There was no comma separating the arguments to AS_HELP_STRING, so it
   appeared as one long string.
2. autoconf builds the help text when generating configure, so shell
   variables such as USE_SIGIO_BY_DEFAULT can't be used. Instead, tell
   the user approximately what the default is.

Signed-off-by: Dan Nicholson <dbn.lists at gmail.com>
---
 configure.ac |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 8c1085b..b2dc0fb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -456,8 +456,8 @@ AC_ARG_ENABLE(debug,         AS_HELP_STRING([--enable-debug],
 AC_ARG_ENABLE(unit-tests,    AS_HELP_STRING([--enable-unit-tests],
                                   [Enable unit-tests (default: auto)]),
                                 [UNITTESTS=$enableval], [UNITTESTS=auto])
-AC_ARG_ENABLE(use-sigio-by-default, AS_HELP_STRING([--enable-use-sigio-by-default]
-  [Enable SIGIO input handlers by default (default: $USE_SIGIO_BY_DEFAULT)]),
+AC_ARG_ENABLE(use-sigio-by-default, AS_HELP_STRING([--enable-use-sigio-by-default],
+  [Enable SIGIO input handlers by default (default: enabled on supported platforms)]),
                                 [USE_SIGIO_BY_DEFAULT=$enableval], [])
 AC_ARG_WITH(int10,           AS_HELP_STRING([--with-int10=BACKEND], [int10 backend: vm86, x86emu or stub]),
 				[INT10="$withval"],
-- 
1.6.6