Set DFU bootloader name

Fixes #22

Each (dfu) interface may have more than one a ltsetting each with their own index and name. According to the DFU_1.1 pdf section 4.2.3, "* Alternate settings can be used by an application to access additional memory segments. In this case,
it is suggested that each alternate setting employ a string descriptor to indicate the target memory
segment; e.g., 'EEPROM'." Whether or not we end up using multiple memory segments it is still good to have a descriptive name incase there are other dfu devices connected.

Edit: Fixed previous indentation

Bootloader/_buildvars.h

@@ -32,6 +32,7 @@
 #define STR_MANUFACTURER	u"Kiibohd"
 #define STR_PRODUCT		u"Kiibohd DFU Bootloader"
 #define STR_SERIAL              u"@CHIP@"
+#define STR_ALTNAME              u"@BOOT_DFU_ALTNAME@"
 
 
 // Mac OS-X and Linux automatically load the correct drivers.  On