Update .gitignore to exclude additional files

Added entries to ignore unpacked dependencies and generated files based on @fabianegli's commit 6ff3c0.

Author: jke000

.gitignore

@@ -1,3 +1,13 @@
+# ignore unpacked shipped dependencies
+MSToolkit/extern/zlib-1.3.1/
+MSToolkit/extern/expat-2.2.9/
+
+# ignore dynamically generated files
+MSToolkit/include/expat.h
+MSToolkit/include/expat_external.h
+MSToolkit/include/zconf.h
+MSToolkit/include/zlib.h
+
 .DS_Store
 .idea
 *.log
@@ -140,4 +150,4 @@ ipch/
 *.msi
 *.msix
 *.msm
-*.msp
+*.msp