Revert "Generate error constants as XCB_BAD_*, similar to Xlib."

Since several extensions named their errors like "BadFoo", this patch
results in names like XCB_EXT_BAD_BAD_FOO, which is really awful. Those
extensions are already kind of awful, as they produce structure names
like xcb_ext_bad_foo_error_t, which is redundant.

A patch that removes "Bad" from the XML extension descriptions, while
maintaining API and ABI compatibility in XCB, is needed before this
patch can be released.

This reverts commit 158c9b6ba1.

src/c-client.xsl

@@ -449,11 +449,6 @@ authorization from the authors.
         </xsl:when>
       </xsl:choose>
     </xsl:variable>
-    <xsl:choose>
-      <xsl:when test="self::error|self::errorcopy">
-        <constant type="number" name="{xcb:xcb-prefix(concat('Bad', @name))}" value="{@number}" />
-      </xsl:when>
-    </xsl:choose>
     <constant type="number" name="{xcb:xcb-prefix(@name)}" value="{@number}" />
     <xsl:choose>
       <xsl:when test="self::event|self::error">