Fix build against xorg-server >= 1.20.

Patch taken from upstream:
https://cgit.freedesktop.org/xorg/driver/xf86-video-savage/commit/?id=0ece556daa8a88771b669d8104396abd9166d2d0

diff --git a/src/savage_driver.c b/src/savage_driver.c
index 58a294d..3cda923 100644
--- a/src/savage_driver.c
+++ b/src/savage_driver.c
@@ -2034,8 +2034,6 @@ static Bool SavagePreInit(ScrnInfoPtr pScrn, int flags)
     xf86DrvMsg(pScrn->scrnIndex, X_PROBED, "Detected current MCLK value of %1.3f MHz\n",
 	       mclk / 1000.0);
 
-    pScrn->maxHValue = 2048 << 3;	/* 11 bits of h_total 8-pixel units */
-    pScrn->maxVValue = 2048;		/* 11 bits of v_total */
     pScrn->virtualX = pScrn->display->virtualX;
     pScrn->virtualY = pScrn->display->virtualY;
 
@@ -3637,6 +3635,14 @@ static ModeStatus SavageValidMode(SCRN_ARG_TYPE arg, DisplayModePtr pMode,
        (pMode->VDisplay > psav->PanelY)))
 	    return MODE_PANEL;
 
+    /* 11 bits of h_total 8-pixel units */
+    if (pMode->HTotal > (2048 << 3))
+	return MODE_BAD_HVALUE;
+
+    /* 11 bits of v_total */
+    if (pMode->VTotal > 2048)
+	return MODE_BAD_VVALUE;
+
     if (psav->UseBIOS) {
 	refresh = SavageGetRefresh(pMode);
         return (SavageMatchBiosMode(pScrn,pMode->HDisplay,
m?id=f37e2388d0b777793a711c817a7ee0826d8cdc9f'>tree</a><a href='/guix/commit/tests/offload.scm?id=f37e2388d0b777793a711c817a7ee0826d8cdc9f'>commit</a><a href='/guix/diff/tests/offload.scm?id=f37e2388d0b777793a711c817a7ee0826d8cdc9f'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/tests/offload.scm'>
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<div class='path'>path: <a href='/guix/log/?id=f37e2388d0b777793a711c817a7ee0826d8cdc9f'>root</a>/<a href='/guix/log/tests?id=f37e2388d0b777793a711c817a7ee0826d8cdc9f'>tests</a>/<a href='/guix/log/tests/offload.scm?id=f37e2388d0b777793a711c817a7ee0826d8cdc9f'>offload.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/offload.scm?id=f37e2388d0b777793a711c817a7ee0826d8cdc9f&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-08-25 13:45:27 -0400'>2020-08-25</span></td><td><a href='/guix/commit/tests/offload.scm?id=4b5a6fbc9b754c0ca70d033dd99f17c4f028733a'>offload: Modify the build-machine record to accept multiple systems.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/offload.scm (&lt;build-machine&gt;)[systems]: New field.
[system]: Accessor changed to %build-machine-system.  Default to #f.
* guix/scripts/offload.scm (build-machine-system): Wrap %build-machine-system
with a deprecation warning.
(build-machine-systems): Access the new systems field or fallback to use
build-machine-system, for backward compatibility.
(machine-matches?): Adjust.
* tests/offload.scm: Add tests...
* Makefile.am (SCM_TESTS): ...and register them.
* doc/guix.texi (Daemon Offload Setup): Update doc.
</span></span></td><td>Maxim Cournoyer</td></tr>