Windows installer: Update SBCL.
Windows: Update TCL/TK to 9.0.3.
Remove SCL from README-lisps.md.
SBCL (not SCL) code was removed in commit 5e51fb89.
Remove SCL code from src/Makefile.am and tests/Makefile.am.
SBCL (not SCL) code was removed in commit ea4518bc2.
Fix some typos.
Use Subresource Integrity for external CSS and JS files.