* New menu option to minimize BSSL ROM with only RSA
Adds a menu option and define to limit BearSSL to older RSA connection
options. This saves ~45K program memory and can speed up connections
since EC, while more secure, is significantly slower on the chip.
The supported ciphers are identical to the ones that axTLS supported.
Fixes#6005
* Add default SSLFLAGS(blank) to platform.txt
* Fix unused variable warning
* Add clarifying comment to menu items