[M] Change in coreboot[main]: lib/string: Add strncat() and strcat() functions

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Jakub Czapiga, Julius Werner.

Yu-Ping Wu has posted comments on this change by Yu-Ping Wu. ( https://review.coreboot.org/c/coreboot/+/83765?usp=email )

Change subject: lib/string: Add strncat() and strcat() functions
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Patch Set 4:

(2 comments)

Patchset:

PS3:
> Maybe at least start something in commonlib with these two functions (doesn't mean you have to port everything else right away too)?

Sure. I can do that.

File src/lib/string.c:

https://review.coreboot.org/c/coreboot/+/83765/comment/71e68dfd_abde9edd?usp... :
PS4, Line 119: 	strcpy(dst + strlen(dst), src);
> Same applies here, obviously (same code as above just without the `count--` check).

I still don't understand the problem of the current implementation. If I write

```
char *ptr = dst + strlen(dst);
while (*src)
    *ptr++ = *src++;
*ptr = '\0';
```

isn't that exactly equivalent to calling `strcpy()`?