add a clangd and qtcreator make targets

Add a clangd make target:
$ make clangd
This installs a .clangd file with configuration (includes/macros/compiler flags)
for the clandg language server.

Add a qtcreator make target:
$ make qtcreator
This installs a .qtcreator directory with QTCreator IDE project files.
In the QTCreator you can open a project by selecting the .qtcreator/tito.creator
file.

You can use 'make qtcreator' again to refresh .qtcreator/tito.files,
the rest of the project files will not be modified.

.gitignore

@@ -3,12 +3,6 @@
 .settings/
 *.o
 *.a
-.clangd
-.qtc_clangd/
-tito.cflags
-tito.config
-tito.creator
-tito.creator.user
-tito.cxxflags
-tito.files
-tito.includes
+/.clangd
+/.qtcreator/
+/.qtc_clangd/