Unreviewed. Update OptionsGTK.cmake and NEWS for 2.51.91 release

* Source/WebKit/gtk/NEWS: Add release notes for 2.51.91.
* Source/cmake/OptionsGTK.cmake: Bump version numbers.

Source/WebKit/gtk/NEWS

diff --git a/Source/WebKit/gtk/NEWS b/Source/WebKit/gtk/NEWS
index 97fc18e..e33215e 100644
--- a/Source/WebKit/gtk/NEWS
+++ b/Source/WebKit/gtk/NEWS
@@ -1,4 +1,17 @@
 =================
+WebKitGTK 2.51.91
+=================
+
+What's new in WebKitGTK 2.51.91?
+
+  - Disable GPU process by default.
+  - Improve async scrolling when main thread is busy by avoiding locks and rendering the
+    scrollbars from the scrolling thread.
+  - Fix the build with old versions of libdrm.
+  - Fix the build on i386.
+  - Fix several crashes and rendering issues.
+
+=================
 WebKitGTK 2.51.90
 =================
 

Source/cmake/OptionsGTK.cmake

diff --git a/Source/cmake/OptionsGTK.cmake b/Source/cmake/OptionsGTK.cmake
index 3ce7869..c4351a9 100644
--- a/Source/cmake/OptionsGTK.cmake
+++ b/Source/cmake/OptionsGTK.cmake
@@ -3,7 +3,7 @@
 
 WEBKIT_OPTION_BEGIN()
 
-SET_PROJECT_VERSION(2 51 90)
+SET_PROJECT_VERSION(2 51 91)
 
 set(USER_AGENT_BRANDING "" CACHE STRING "Branding to add to user agent string")
 
@@ -191,11 +191,11 @@
 EXPOSE_STRING_VARIABLE_TO_BUILD(WEBKITGTK_API_VERSION)
 
 if (WEBKITGTK_API_VERSION VERSION_EQUAL "4.1")
-    CALCULATE_LIBRARY_VERSIONS_FROM_LIBTOOL_TRIPLE(WEBKIT 21 0 21)
-    CALCULATE_LIBRARY_VERSIONS_FROM_LIBTOOL_TRIPLE(JAVASCRIPTCORE 10 4 10)
+    CALCULATE_LIBRARY_VERSIONS_FROM_LIBTOOL_TRIPLE(WEBKIT 21 1 21)
+    CALCULATE_LIBRARY_VERSIONS_FROM_LIBTOOL_TRIPLE(JAVASCRIPTCORE 10 5 10)
 elseif (WEBKITGTK_API_VERSION VERSION_EQUAL "6.0")
-    CALCULATE_LIBRARY_VERSIONS_FROM_LIBTOOL_TRIPLE(WEBKIT 20 0 16)
-    CALCULATE_LIBRARY_VERSIONS_FROM_LIBTOOL_TRIPLE(JAVASCRIPTCORE 8 4 7)
+    CALCULATE_LIBRARY_VERSIONS_FROM_LIBTOOL_TRIPLE(WEBKIT 20 1 16)
+    CALCULATE_LIBRARY_VERSIONS_FROM_LIBTOOL_TRIPLE(JAVASCRIPTCORE 8 5 7)
 else ()
     message(FATAL_ERROR "Unhandled API version")
 endif ()