v1.87

Bump version to 1.87

Cuts the v1.87 release. The Version Tagging job tags the commit where
project(SURELOG VERSION ...) changes, so merging this creates v1.87.

Also moves the UHDM submodule to UHDM master at v1.87 (chipsalliance/UHDM#1143).
Surelog and UHDM version numbers go in tandem -- Surelog.pc.in pins
"Requires: UHDM >= @PROJECT_VERSION@" -- so a Surelog 1.87 that pinned a
UHDM still calling itself 1.86 would fail its own pkg-config check.

The submodule moves by exactly two commits, UHDM's version bump and its
merge, so no UHDM behavior changes here.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>