Merge remote-tracking branch 'origin/pr/2637' into mbedtls-2.16

* origin/pr/2637:
  Only use submodule if present
diff --git a/.gitignore b/.gitignore
index f40064d..789f57e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,8 +1,20 @@
+# Random seed file created by test scripts and sample programs
+seedfile
+
+# CMake build artifacts:
 CMakeCache.txt
 CMakeFiles
 CTestTestfile.cmake
 cmake_install.cmake
 Testing
+# CMake generates *.dir/ folders for in-tree builds (used by MSVC projects), ignore all of those:
+*.dir/
+# MSVC files generated by CMake:
+/*.sln
+/*.vcxproj
+/*.filters
+
+# Test coverage build artifacts:
 Coverage
 *.gcno
 *.gcda
@@ -10,11 +22,6 @@
 # generated by scripts/memory.sh
 massif-*
 
-# MSVC files generated by CMake:
-/*.sln
-/*.vcxproj
-/*.filters
-
 # MSVC build artifacts:
 *.exe
 *.pdb
@@ -24,5 +31,13 @@
 # Python build artifacts:
 *.pyc
 
-# CMake generates *.dir/ folders for in-tree builds (used by MSVC projects), ignore all of those:
-*.dir/
+# Generated documentation:
+/apidoc
+
+# Editor navigation files:
+/GPATH
+/GRTAGS
+/GSYMS
+/GTAGS
+/TAGS
+/tags
diff --git a/.globalrc b/.globalrc
new file mode 100644
index 0000000..01b2ea5
--- /dev/null
+++ b/.globalrc
@@ -0,0 +1,3 @@
+default:\
+    :langmap=c\:.c.h.function:\
+
diff --git a/Makefile b/Makefile
index f4c0a00..1ae6bd9 100644
--- a/Makefile
+++ b/Makefile
@@ -120,3 +120,12 @@
 apidoc_clean:
 	rm -rf apidoc
 endif
+
+## Editor navigation files
+C_SOURCE_FILES = $(wildcard include/*/*.h library/*.[hc] programs/*/*.[hc] tests/suites/*.function)
+tags: $(C_SOURCE_FILES)
+	ctags -o $@ $(C_SOURCE_FILES)
+TAGS: $(C_SOURCE_FILES)
+	etags -o $@ $(C_SOURCE_FILES)
+GPATH GRTAGS GSYMS GTAGS: $(C_SOURCE_FILES)
+	ls $(C_SOURCE_FILES) | gtags -f - --gtagsconf .globalrc