TeX-run-discard-or-function: allow lisp expressions
Fix crash when handling NS_MOUSEDRAG_EVENT events

Crash occurred when mousedrag event was received as first system event
after startup, as KVAR (current_kboard, system_key_syms) was not
initialized and modify_event_symbol was not equipped to handle alist
type caches, which are assigned negative or infinite size in the
function call to modify_event_symbol.
fix: drag colors to fringe
Mention fix to AUCTeX preview size in changelog