Add a -showDefaultModulePath option.

As discussed on the mailing list, people would rather have an X command-line
option to print the module path so installers can know where to put modules,
rather than the installers using `pkg-config --variable=moduledir xorg-server`,
since some distros choose not to install xorg-server.pc.
(cherry picked from 0a2a6e4070 commit)

hw/xfree86/common/xf86Init.c

@@ -100,6 +100,7 @@
 
 static void xf86PrintBanner(void);
 static void xf86PrintMarkers(void);
+static void xf86PrintDefaultModulePath(void);
 static void xf86RunVtInit(void);
 
 #ifdef __UNIXOS2__
@@ -1488,6 +1489,11 @@ ddxProcessArgument(int argc, char **argv, int i)
     xf86PrintBanner();
     exit(0);
   }
+  if (!strcmp(argv[i],"-showDefaultModulePath"))
+  {
+    xf86PrintDefaultModulePath();
+    exit(0);
+  }
   /* Notice the -fp flag, but allow it to pass to the dix layer */
   if (!strcmp(argv[i], "-fp"))
   {
@@ -1737,6 +1743,7 @@ ddxUseMsg()
   ErrorF("-ignoreABI             make module ABI mismatches non-fatal\n");
   ErrorF("-isolateDevice bus_id  restrict device resets to bus_id (PCI only)\n");
   ErrorF("-version               show the server version\n");
+  ErrorF("-showDefaultModulePath show the server default module path\n");
   /* OS-specific usage */
   xf86UseMsg();
   ErrorF("\n");
@@ -1859,6 +1866,12 @@ xf86PrintMarkers()
   LogPrintMarkers();
 }
 
+static void
+xf86PrintDefaultModulePath(void)
+{
+  ErrorF("%s\n", DEFAULT_MODULE_PATH);
+}
+
 static void
 xf86RunVtInit(void)
 {

hw/xfree86/doc/man/Xorg.man.pre

@@ -426,6 +426,9 @@ Print out the server version, patchlevel, release date, the operating
 system/platform it was built on, and whether it includes module loader
 support.
 .TP 8
+.B \-showDefaultModulePath
+Print out the default module path the server was compiled with.
+.TP 8
 .BI \-config " file"
 Read the server configuration from
 .IR file .