v1.5.0: Bump version

Many improvements over v1.4.0 (too long since last version update), mainly:

* Stabilization fixes for custom interrupt handlers: avoid kernel panics by
  making sure the virtual address of the interrupt handler in the IDT is
  _always_ accessible, even when interrupting the kernel (KPTI address space)
  or after context switching to another process (via persistent shadow mapping
  in the kernel address space). Thanks @0xhilbert!
* Experimental Gramine port. Thanks @aegis2501!
* Support for Load Value Injection (LVI) attacks.
* Support for sending inter-processor interrupts through the local APIC.
* APIC precision microbenchmarks (AEX-Notify paper).
* Improve documentation.

README.md

@@ -20,8 +20,9 @@ Gardner at a Gallop" photo series, which, like our enclave single-stepping
 goal, breaks down the galloping horse dynamics into a series of individual
 photo frames to reveal overall horse gait properties.
 
-| SGX-Step release | Comments                                                                       |
+| SGX-Step release | Changelog features                                                             |
 | ---------------- | ------------------------------------------------------------------------------ |
+| v1.5.0           | Stabilization fixes (KPTI, kernel ISR mapping); (experimental) Gramine port; IPI support. |
 | v1.4.0           | Privileged interrupt/call gates (Plundervolt).                                 |
 | v1.3.0           | Transient-execution support (Foreshadow).                                      |
 | v1.2.0           | User-space interrupt handling and deterministic zero-step filtering (Nemesis). |