build: improve description of --enable-lpeg configure option

It links lpeg statically into the vis binary, meaning it does not need
to be dlopen(3)-ed at runtime. While this improves the portability of
the resulting vis binary, it is not necessary to enable this option to
get syntax highlighting support.

Maybe the option should be renamed to avoid further confusion.

configure

@@ -24,7 +24,7 @@ Fine tuning of the installation directories:
 
 Optional features:
   --enable-lua            build with Lua support [auto]
-  --enable-lpeg           build with built-in LPeg support [auto]
+  --enable-lpeg           build with support for statically linking to LPeg [auto]
   --enable-selinux        build with SELinux support [auto]
   --enable-acl            build with POSIX ACL support [auto]