* Upgrade to 2.5.0-4 toolchain w/improved pgm_read_x
Rebuild the entire toolchain (including standard libraries) with the
latest pgm_read_xxx headers included (which fix unaligned dword reads
from progmem and run faster/smaller, and a pgm_read_byte change which
removes an instruction on each read saving flash).
Pull in latest bearssl while we're at it, too, which speeds up EC
handshakes and reduced ROM usage, too.
* Fix C++ exceptions
Exception code now only does 32b aligned reads from progmem to access
the eh_table (some via -mforce-l32, some via hand-inserted pgm_read_x
macros).
Fixes#6151Fixes#6305Fixes#6198
Scripts, makefiles, and users who do no changes will not have exceptions
enabled during builds. This should avoid the sketch inflation issue for
users who are space constrained, while allowing users who care about
exceptions to enable them through the IDE.
