Moved the rest of the longhand structs to separate files.

Sorry for the bulk size of this; I know already it's not going to be a fun thing to review. Nevertheless, it should be done so we finalize the split of this huge file into smaller, more maintable parts.

The content of stuff being moved to separate files is unchanged. Only some minor formatting changes have been made and similar, but nothing of particular interest. IMHO it should be safe to merge if all the tests are fine.

components/style/properties/longhand/svg.mako.rs

@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+<%namespace name="helpers" file="/helpers.mako.rs" />
+
+<% data.new_style_struct("SVG", inherited=False, gecko_ffi_name="nsStyleSVGReset") %>
+
+${helpers.single_keyword("dominant-baseline",
+                 """auto use-script no-change reset-size ideographic alphabetic hanging
+                    mathematical central middle text-after-edge text-before-edge""",
+                 products="gecko")}
+
+${helpers.single_keyword("vector-effect", "none non-scaling-stroke", products="gecko")}
+
+// CSS Masking Module Level 1
+// https://www.w3.org/TR/css-masking-1/
+${helpers.single_keyword("mask-type", "luminance alpha", products="gecko")}