Add coverage ignores (incl personal header-only XCode coverage tests

.gitignore

@@ -1,3 +1,6 @@
+coverage/
+*-test-cov
+# C++.gitignore
 # Compiled Object files
 *.slo
 *.lo
@@ -27,3 +30,9 @@
 *.out
 *.app
 
+# Gcov.gitignore
+# gcc coverage testing tool files
+
+*.gcno
+*.gcda
+*.gcov