configure: disable live555 by default

Latest liblivemedia version disables APIs we need. The code still
exists in the library and the changelog says the old interface can be
enabled with "#define RTSPCLIENT_SYNCHRONOUS_INTERFACE". However, the
code on the library side is disabled by default too, and seems to be
disabled in distro packages, so defining that in the player does not
help (just delays the failure until link time). It's possible the
distro packages will be changed to enable this, but since dropping
live555 support is desirable anyway, change configure to disable
support by default at least for now.

The live555 code is the only part of the source that's in C++.
Including C headers in code compiled as C++ has caused issues at
times, so deleting this code would have a maintenance benefit.
Reportedly the rtsp support in Libav has improved, so there should
be less need for live555.

configure

@@ -335,7 +335,7 @@ Optional features:
   --disable-networking   disable networking [enable]
   --enable-winsock2_h    enable winsock2_h [autodetect]
   --enable-smb           enable Samba (SMB) input [autodetect]
-  --enable-live          enable LIVE555 Streaming Media [autodetect]
+  --enable-live          enable LIVE555 Streaming Media [disable]
   --enable-nemesi        enable Nemesi Streaming Media [autodetect]
   --disable-vcd          disable VCD support [autodetect]
   --disable-bluray       disable Blu-ray support [autodetect]
@@ -634,7 +634,7 @@ _dvdread_internal=auto
 _libdvdcss_internal=auto
 _xanim=auto
 _real=auto
-_live=auto
+_live=no
 _nemesi=auto
 _native_rtsp=yes
 _xinerama=auto
@@ -5745,7 +5745,7 @@ fi
 echores "$_nemesi"
 
 echocheck "LIVE555 Streaming Media libraries"
-if test "$_live" = auto  && test "$networking" = yes ; then
+if test "$_live" != no  && test "$networking" = yes ; then
   cat > $TMPCPP << EOF
 #include <liveMedia.hh>
 #if (LIVEMEDIA_LIBRARY_VERSION_INT < 1141257600)