Merge "Web installer: always autoselect some DB type"

diff --combined RELEASE-NOTES-1.21
index 1930636,5adf80e..f71f1ef
--- 1/RELEASE-NOTES-1.21
--- 2/RELEASE-NOTES-1.21
+++ b/RELEASE-NOTES-1.21
@@@ -115,7 -115,6 +115,7 @@@ production
    uz, vi.
  * Added 'CategoryAfterPageAdded' and 'CategoryAfterPageRemoved' hooks.
  * Added 'HistoryRevisionTools' and 'DiffRevisionTools' hooks.
 +* Added 'SpecialSearchResultsPrepend' and 'SpecialSearchResultsAppend' hooks.
  * (bug 33186) Add image rotation api "imagerotate"
  * (bug 34040) Add "User rights management" link on user page toolbox.
  * (bug 45526) Add QUnit assertion helper "QUnit.assert.htmlEqual" for asserting
@@@ -210,6 -209,8 +210,8 @@@
  * (bug 45143) jquery.badge: Treat non-Latin variants of zero as zero as well.
  * (bug 46151) mwdocgen.php should not ignore exit code of doxygen command.
  * (bug 41889) Fix $.tablesorter rowspan exploding for complex cases.
+ * (bug 47489) Installer now automatically selects the next-best database type if
+   the PHP mysql extension is not loaded, preventing fatal errors in some cases.
  
  === API changes in 1.21 ===
  * prop=revisions can now report the contentmodel and contentformat.