C POSIX library

Exmples under c/posix:

c/posix/signal_return.c: stackoverflow.com/questions/37063212/where-does-signal-handler-return-back-to
c/posix/inet/pton.c: inet_pton demo. Adapted from man inet_pton on Ubuntu 23.04. Usage:
```
./pton.out 192.187.1.42
```
Output:
```
0xc0bb012a
```
So we see that the strings was converted to an integer, e.g.:
- 0xc0 = 192
- 0xbb = 187
- 0x01 = 1
- 0x2a = 42
See also: stackoverflow.com/questions/1680622/ip-address-to-integer-c/76520978#76520978
c/posix/inet/ntop.c: inet_ntop demo. Adapted from man inet_pton on Ubuntu 23.04. Usage:
```
./ntop.out 0x01021AA0
```
Output:
```
./ntop.out 0x01021AA0
```

 Ancestors (10)