Add export and inferred submodule declarations to the libgit2 modulemap

libgit2/module.modulemap

@@ -1,6 +1,9 @@
 module libgit2 {
 	umbrella header "git2.h"
 
+	export *
+	module * { export * }
+
 	// Exclude headers intended only for Microsoft compilers
 	exclude header "git2/inttypes.h"
 	exclude header "git2/stdint.h"
@@ -8,14 +11,21 @@ module libgit2 {
 	// Explicit modules for headers not included in the umbrella header:
 	explicit module cred_helpers {
 		header "git2/cred_helpers.h"
+
+		export *
 	}
 
 	explicit module trace {
 		header "git2/trace.h"
+
+		export *
 	}
 
 	// Explicit module for the "sys" headers:
 	explicit module sys {
 		umbrella "git2/sys"
+
+		export *
+		module * { export * }
 	}
 }