build: Use AS_HELP_STRING macro to format the ./configure --help better

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/configure.in b/configure.in
index e3e178c..140fdc2 100644
--- a/configure.in
+++ b/configure.in
@@ -35,22 +35,34 @@
 AM_CONFIG_HEADER(config.h)
 
 AC_ARG_ENABLE(talloc,
-	[  --disable-talloc Disable building talloc memory allocator ],
+	[AS_HELP_STRING(
+		[--disable-talloc],
+		[Disable building talloc memory allocator]
+	)],
 	[enable_talloc=0], [enable_talloc=1])
 AM_CONDITIONAL(ENABLE_TALLOC, test "x$enable_talloc" = "x1")
 
 AC_ARG_ENABLE(plugin,
-	[  --disable-plugin Disable support for dlopen plugins ],
+	[AS_HELP_STRING(
+		[--disable-plugin],
+		[Disable support for dlopen plugins],
+	)],
 	[enable_plugin=0], [enable_plugin=1])
 AM_CONDITIONAL(ENABLE_PLUGIN, test "x$enable_plugin" = "x1")
 
 AC_ARG_ENABLE(tests,
-	[  --disable-tests Disable building test programs ],
+	[AS_HELP_STRING(
+		[--disable-tests],
+		[Disable building test programs]
+	)],
 	[enable_tests=0], [enable_tests=1])
 AM_CONDITIONAL(ENABLE_TESTS, test "x$enable_tests" = "x1")
 
 AC_ARG_ENABLE(vty,
-	[  --disable-vty Disable building VTY telnet interface ],
+	[AS_HELP_STRING(
+		[--disable-vty],
+		[Disable building VTY telnet interface]
+	)],
 	[enable_vty=0], [enable_vty=1])
 AM_CONDITIONAL(ENABLE_VTY, test "x$enable_vty" = "x1")