[Performance] Slowdown when looking up symbol for targets with many modules

[mistymntncop]

I was debugging Chromium and have been experiencing noticeable slowdowns in the UI sometimes when stepping into a function. Having a deeper look with RemedyBG it seems to happen whenever "e_parse_expr_from_text_tokens__prec" attempts to check if a global variable/thread variable/procedure exists for that symbol. Chromium has over 3000 modules so it potentially has to loop over each module for each of these 3 cases - for every evaluated (non-local/missing) symbol - so I assume this is what is the cause of the slowdown.