Spec: bump version 0.3.1 -> v0.4.0

 On branch master
 Your branch is ahead of 'origin/master' by 3 commits.
   (use "git push" to publish your local commits)

 Changes to be committed:
	modified:   doc/riscv-crypto-spec.tex

 Changes not staged for commit:
	modified:   extern/riscv-gnu-toolchain (modified content)
	modified:   extern/riscv-isa-sim (modified content)

doc/riscv-crypto-spec.tex

@@ -4,7 +4,7 @@
 
 \title{RISC-V Cryptographic Extension Proposals}
 \author{Editors: ???, Ben Marshall}
-\date{Version $0.3.2$ (\today) \\
+\date{Version $0.4.0$ (\today) \\
 \href{https://github.com/scarv/riscv-crypto}{
 {\small \tt git:\import{../build/spec/}{spec.commit}}}
 }