Add some aliases for re-related functions

[Yuan Fu]

While debating whether it’s effective to add prefixes to increase 
discoverability, lets start with incremental and uncontroversial changes. Let’s 
start from re-related functions since it seems that many people agree on this. 
Here is a list of functions that I think could benefit from an alias. 

replace-regexp-in-string        re-replace-in-string
replace-match                   re-replace-match
string-match                    re-search-in-string
string-match-p                  re-match-in-string-p
match-string                    re-matched-string
match-string-no-properties      re-matched-string-no-properties
match-beginning                 re-match-beginning
match-end                       re-match-end

looking-at                      re-match-after-point
looking-back                    re-match-before-point
looking-at-p                    re-match-after-point-p
posix-search-forward            re-posix-search-forward
posix-search-backward           re-posix-search-backward
posix-looking-at                re-posix-looking-at
posix-search-in-string          re-posix-search-in-string

Let’s do it like this: if you don’t like adding alias to a certain function 
(strongly), call it out and we will remove it from the list for now. Then we 
should have a small list that everybody agrees upon (or at least no one 
absolutely hates). 

And please do not drift the topic away in this thread, which hinders the 
original purpose of the thread. Let’s focus on these functions and only these 
functions.

Yuan