Make socket directory configurable, don't hardcode /tmp/.xrdp

Use XRDP_SOCKET_PATH in file_loc.h

Don't define any non-socket paths in file_loc.h, they should come from
the makefiles.

Define all paths unconditionally, they should not be defined elsewhere.

Pass XRDP_SOCKET_PATH as environment variable to the backends.

docs/man/Makefile.am

@@ -17,7 +17,8 @@ SUBST_VARS = sed \
    -e 's|@PACKAGE_VERSION[@]|$(PACKAGE_VERSION)|g' \
    -e 's|@bindir[@]|$(bindir)|g' \
    -e 's|@localstatedir[@]|$(localstatedir)|g' \
-   -e 's|@sysconfdir[@]|$(sysconfdir)|g'
+   -e 's|@sysconfdir[@]|$(sysconfdir)|g' \
+   -e 's|@socketdir[@]|$(socketdir)|g'
 
 subst_verbose = $(subst_verbose_@AM_V@)
 subst_verbose_ = $(subst_verbose_@AM_DEFAULT_V@)

docs/man/xrdp-chansrv.8.in

@@ -30,10 +30,10 @@ Dynamic Virtual Channel
 
 .SH FILES
 .TP
-.I /tmp/.xrdp/xrdp_chansrv_socket_*
+.I @socketdir@/xrdp_chansrv_socket_*
 UNIX socket used by external programs to implement channels.
 .TP
-.I /tmp/.xrdp/xrdp_api_*
+.I @socketdir@/xrdp_api_*
 UNIX socket used by \fBxrdp\-chansrv\fP to communicate with \fBxrdp\-sesman\fP.
 .TP
 .I $XDG_DATA_HOME/xrdp/xrdp-chansrv.log

docs/man/xrdp-dis.1.in

@@ -16,7 +16,7 @@ to get the default host and display number.
 
 .SH FILES
 .TP
-.I /tmp/.xrdp/xrdp_disconnect_display_*
+.I @socketdir@/xrdp_disconnect_display_*
 UNIX socket used to communicate with the \fBxrdp\fP(8) session manager.
 
 .SH KNOWN ISSUES