Parameterise the sockdir with the UID of the user

The top level socket directory is now called XRDP_SOCKET_ROOT_PATH.
Below that are user-specific directories referred to with the
XRDP_SOCKET_PATH macro - this name is hard-coded into xorgxrdp and
the audio modules as an environment variable.

XRDP_SOCKET_PATH now looks like $XRDP_SOCKET_ROOT_PATH/<uid>

XRDP_SOCKET_PATH is only writeable by the user, and readable by the user
and the xrdp process.

xrdpapi/Makefile.am

@@ -4,7 +4,7 @@ EXTRA_DIST = \
   vrplayer.mk
 
 AM_CPPFLAGS = \
-  -DXRDP_SOCKET_PATH=\"${socketdir}\" \
+  -DXRDP_SOCKET_ROOT_PATH=\"${socketdir}\" \
   -I$(top_srcdir)/common
 
 module_LTLIBRARIES = \

xrdpapi/xrdpapi.c

@@ -140,7 +140,7 @@ WTSVirtualChannelOpenEx(unsigned int SessionId, const char *pVirtualName,
     memset(&s, 0, sizeof(struct sockaddr_un));
     s.sun_family = AF_UNIX;
     bytes = sizeof(s.sun_path);
-    snprintf(s.sun_path, bytes - 1, CHANSRV_API_STR, wts->display_num);
+    snprintf(s.sun_path, bytes - 1, CHANSRV_API_STR, getuid(), wts->display_num);
     s.sun_path[bytes - 1] = 0;
     bytes = sizeof(struct sockaddr_un);