devel-docs: add performance-logs documentation

Add devel-docs/performance-logs/performance-logs.md, which
describes how to record and view performance logs, and how to
report perofrmance-related issues.

(cherry picked from commit fa9161e4)

configure.ac

@@ -2917,6 +2917,7 @@ devel-docs/libgimpthumb/Makefile
 devel-docs/libgimpthumb/version
 devel-docs/libgimpwidgets/Makefile
 devel-docs/libgimpwidgets/version
+devel-docs/performance-logs/Makefile
 devel-docs/tools/Makefile
 docs/Makefile
 menus/Makefile

devel-docs/Makefile.am

@@ -14,7 +14,9 @@ SUBDIRS = \
 	libgimpthumb	\
 	libgimpwidgets	\
 	libgimp		\
-	$(app)
+	$(app)		\
+	\
+	performance-logs
 
 EXTRA_DIST = \
 	README				\

devel-docs/debugging-tips.txt

@@ -93,3 +93,8 @@ variable GIMP_PLUGIN_DEBUG.
 
 The CLI option --stack-trace-mode also applies to plug-ins, in order to
 output a back trace on terminal.
+
+## Performance logs ##
+
+See file `devel-docs/performance-logs/performance-logs.md` for information
+about GIMP performance logs, which can help during optimization.

devel-docs/performance-logs/.gitignore

+/Makefile
+/Makefile.in

devel-docs/performance-logs/Makefile.am

+## Process this file with automake to produce Makefile.in
+
+EXTRA_DIST = \
+	dashboard-add-marker.png	\
+	dashboard-start-recoriding.png	\
+	dashboard-stop-recording.png	\
+	new-performance-issue.png	\
+	performance-log-viewer.png	\
+	performance-logs.md