configure: Disable ext_delta_q if delta_q disabled

Builds will fail if configured with delta_q disabled and ext_delta_q not
also disabled, since ext_delta_q is soft enabled. This patch fixes this
by making the configure script disable ext_delta_q if delta_q is not
enabled.

Change-Id: Ic060ebae9a949650964081f25bf9e72bfc8e7a14

configure

diff --git a/configure b/configure
index 83ec996..828dc62 100755
--- a/configure
+++ b/configure
@@ -518,6 +518,10 @@
     enabled ext_delta_q && soft_enable delta_q
     enabled txk_sel && soft_enable lv_map
     enabled compound_round && soft_enable convolve_round
+    if ! enabled delta_q && enabled ext_delta_q; then
+      log_echo "ext_delta_q requires delta_q, so disabling ext_delta_q"
+      disable_feature ext_delta_q
+    fi
     if enabled rawbits && ! enabled daala_ec; then
       log_echo "rawbits requires daala_ec, so disabling rawbits"
       disable_feature rawbits