Doc: Update Meson screenshots

And add alt text for them.

Task-number: QTCREATORBUG-26278
Change-Id: Ibe40f284e3162a77982fc3731313a6f2bc9492b5
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

doc/qtcreator/src/meson/creator-projects-meson-building.qdoc

@@ -29,7 +29,7 @@
 
     \title Meson Build Configuration
 
-    \image qtcreator-meson-build-settings.png
+    \image qtcreator-meson-build-settings.png "Meson build settings"
 
     Settings are grouped by category by Meson. All items are user modifiable
     except \c backend which is forced to Ninja, \c {buildtype}, \c debug as well
@@ -45,6 +45,8 @@
     \note Any modified setting will remain in bold until \uicontrol
     {Apply configuration changes} is selected.
 
+    For more information about using Meson, see \l{Setting Up Meson}.
+
     \section1 Meson Build Steps
 
     \QC builds Meson projects by running \c {ninja -v target}.
@@ -52,7 +54,7 @@
     You can add arguments and targets for the build command in
     \uicontrol {Build Steps}.
 
-    \image qtcreator-meson-build-steps.png
+    \image qtcreator-meson-build-steps.png "Meson build steps"
 
     The build errors and warnings are parsed and displayed in the
     \uicontrol Issues output pane.
@@ -62,7 +64,7 @@
     When building with Meson, you can add arguments and targets for the clean
     command in \uicontrol {Clean Steps}.
 
-    \image qtcreator-meson-clean-steps.png
+    \image qtcreator-meson-clean-steps.png "Meson clean steps"
 
     The build errors and warnings are parsed and displayed in the
     \uicontrol Issues output pane.

doc/qtcreator/src/meson/creator-projects-meson.qdoc

@@ -73,7 +73,7 @@
     \uicontrol Tools > \uicontrol Options > \uicontrol Kits > \uicontrol Kits
     tab to add the Meson and Ninja tools to a build and run kit:
 
-    \image qtcreator-kits.png
+    \image qtcreator-kits-meson.png "Setting Meson executable in Kit options"
 
     For more information, see \l {Adding Kits}.