Earliest version bootloaders (128K v2.0, 32K v1.0) might use 'return' global vars for something else

[basilhussain]

The earliest versions of RAM erase/write routines (128K v2.0 and 32K v1.0) do not check whether a write has been attempted to a protected page (by checking WR_PG_DIS flag of FLASH_IAPSR register like later versions do), and so consequently do not have 'return' global variables (i.e. global_0x9b and global_0x9c) that they set the value of.

We need to check whether it is safe to still set the contents of the aforementioned global variables when running from these earliest bootloader versions. Examining the disassembly of a dump of the bootloader ROM from these versions will be the easiest way to tell.