changes in sbcl-1.5.2 relative to sbcl-1.5.1:
* enhancement: RISC-V support with the generational garbage collector.
* enhancement: command-line option "--tls-limit" can be used to alter the
maximum number of thread-local symbols from its default of 4096.
* enhancement: better muffling of redefinition and lambda-list warnings
* platform support:
- OS X: use Grand Central Dispatch semaphores, rather than Mach semaphores
- Windows: remove non-functional definition of make-listener-thread
* new feature: decimal reader syntax for rationals, using the R exponent
marker and/or *READ-DEFAULT-FLOAT-FORMAT* of RATIONAL.
* optimization: various Unicode tables have been packed more efficiently