RelNotes 2.20: move some items between sections

Some items that should be in "Performance, Internal Implementation,
Development Support etc." have ended up in "UI, Workflows & Features"
and "Fixes since v2.19". Move them, and do s/uses/use/ while at it.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/RelNotes/2.20.0.txt

@@ -137,11 +137,6 @@ UI, Workflows & Features
    command line, or setting sendemail.suppresscc configuration
    variable to "misc-by", can be used to disable this behaviour.
 
- * Developer builds now uses -Wunused-function compilation option.
-
- * One of our CI tests to run with "unusual/experimental/random"
-   settings now also uses commit-graph and midx.
-
  * "git mergetool" learned to take the "--[no-]gui" option, just like
    "git difftool" does.
 
@@ -185,6 +180,11 @@ UI, Workflows & Features
 
 Performance, Internal Implementation, Development Support etc.
 
+ * Developer builds now use -Wunused-function compilation option.
+
+ * One of our CI tests to run with "unusual/experimental/random"
+   settings now also uses commit-graph and midx.
+
  * When there are too many packfiles in a repository (which is not
    recommended), looking up an object in these would require
    consulting many pack .idx files; a new mechanism to have a single
@@ -387,6 +387,14 @@ Performance, Internal Implementation, Development Support etc.
    two classes to ease code migration process has been proposed and
    its support has been added to the Makefile.
 
+ * The "container" mode of TravisCI is going away.  Our .travis.yml
+   file is getting prepared for the transition.
+   (merge 32ee384be8 ss/travis-ci-force-vm-mode later to maint).
+
+ * Our test scripts can now take the '-V' option as a synonym for the
+   '--verbose-log' option.
+   (merge a5f52c6dab sg/test-verbose-log later to maint).
+
 
 Fixes since v2.19
 -----------------
@@ -544,14 +552,6 @@ Fixes since v2.19
    didn't make much sense.  This has been corrected.
    (merge 669b1d2aae md/exclude-promisor-objects-fix later to maint).
 
- * The "container" mode of TravisCI is going away.  Our .travis.yml
-   file is getting prepared for the transition.
-   (merge 32ee384be8 ss/travis-ci-force-vm-mode later to maint).
-
- * Our test scripts can now take the '-V' option as a synonym for the
-   '--verbose-log' option.
-   (merge a5f52c6dab sg/test-verbose-log later to maint).
-
  * A regression in Git 2.12 era made "git fsck" fall into an infinite
    loop while processing truncated loose objects.
    (merge 18ad13e5b2 jk/detect-truncated-zlib-input later to maint).