bug#22589: 25.0.90; First match found by isearch-forward-symbol is not necessarily a symbol.

[Juri Linkov <juri@linkov.net>]

> Instructions to reproduce:
>
> 1) emacs -Q
> 2) open a new file called "test.c"
> 3) enter this text:
>
> int main() {
>   int i = 0;
>   return 0;
> }
>
> 4) go to the beginning of the buffer
> 5) hit M-s _ and search for the symbol "i"
>
> ---> The very first character in "int main" is highlighted as a match
>      even though the first match should be "i" in "int i =0".

Please imagine that you need to search for the symbol "int"
(or any other symbol longer than the single-character "i").
How then you would be able to type the whole symbol "int"
if the search failed after typing the first character "i"
(or moved to the first occurrence of the symbol "i"
when you need to find the symbol "int")?