Implemented DirAccess get_drive and get_drive_count for OS X

platform/osx/dir_access_osx.h

@@ -46,6 +46,9 @@
 class DirAccessOSX : public DirAccessUnix {
 protected:
 	virtual String fix_unicode_name(const char *p_name) const;
+
+	virtual int get_drive_count();
+	virtual String get_drive(int p_drive);
 };
 
 #endif //UNIX ENABLED

platform/osx/dir_access_osx.mm

@@ -33,7 +33,8 @@
 
 #include <errno.h>
 
-#include <Foundation/NSString.h>
+#include <AppKit/NSWorkspace.h>
+#include <Foundation/Foundation.h>
 
 String DirAccessOSX::fix_unicode_name(const char *p_name) const {
 
@@ -45,4 +46,19 @@ String DirAccessOSX::fix_unicode_name(const char *p_name) const {
 	return fname;
 }
 
+int DirAccessOSX::get_drive_count() {
+	NSArray *vols = [[NSWorkspace sharedWorkspace] mountedLocalVolumePaths];
+	return [vols count];
+}
+
+String DirAccessOSX::get_drive(int p_drive) {
+	NSArray *vols = [[NSWorkspace sharedWorkspace] mountedLocalVolumePaths];
+	int count = [vols count];
+
+	ERR_FAIL_INDEX_V(p_drive, count, "");
+
+	NSString *path = vols[p_drive];
+	return String([path UTF8String]);
+}
+
 #endif //posix_enabled