Ports: Add readline

Ports/AvailablePorts.md

@@ -94,6 +94,7 @@ Please make sure to keep this list up to date when adding and updating ports. :^
 | [`pt2-clone`](pt2-clone/)              | ProTracker 2 clone                                         | 1.28                     | https://github.com/8bitbubsy/pt2-clone                                         |
 | [`python3`](python3/)                  | Python                                                     | 3.9.4                    | https://www.python.org/                                                        |
 | [`quake`](quake/)                      | Quake                                                      | 0.65                     | https://github.com/SerenityOS/SerenityQuake                                    |
+| [`readline`](readline/)                | GNU Readline Library                                       | 8.1                      | https://tiswww.case.edu/php/chet/readline/rltop.html                           |
 | [`rsync`](rsync/)                      | rsync                                                      | 3.1.3                    | https://rsync.samba.org/                                                       |
 | [`scummvm`](scummvm/)                  | ScummVM                                                    | 2.2.0                    | https://www.scummvm.org/                                                       |
 | [`SDL2`](SDL2/)                        | Simple DirectMedia Layer (SDL2)                            |                          | https://github.com/SerenityOS/SDL                                              |

Ports/readline/package.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env -S bash ../.port_include.sh
+
+port=readline
+version=8.1
+useconfigure=true
+files="https://ftpmirror.gnu.org/gnu/readline/readline-${version}.tar.gz readline-${version}.tar.gz
+https://ftpmirror.gnu.org/gnu/readline/readline-${version}.tar.gz.sig readline-${version}.tar.gz.sig
+https://ftpmirror.gnu.org/gnu/gnu-keyring.gpg gnu-keyring.gpg"
+auth_type="sig"
+auth_opts="--keyring ./gnu-keyring.gpg readline-${version}.tar.gz.sig"

Ports/readline/patches/fix-autoconf.patch

@@ -0,0 +1,11 @@
+--- readline-8.1/support/config.sub	2021-04-25 15:47:03.098432900 +0200
++++ readline-8.1/support/config.sub	2021-04-25 15:49:34.874324300 +0200
+@@ -1690,7 +1690,7 @@
+ 	# Now accept the basic system types.
+ 	# The portable systems comes first.
+ 	# Each alternative MUST end in a * to match a version number.
+-	gnu* | android* | bsd* | mach* | minix* | genix* | ultrix* | irix* \
++	gnu* | android* | bsd* | mach* | minix* | genix* | ultrix* | irix* | serenity* \
+ 	     | *vms* | esix* | aix* | cnk* | sunos | sunos[34]* \
+ 	     | hpux* | unos* | osf* | luna* | dgux* | auroraux* | solaris* \
+ 	     | sym* |  plan9* | psp* | sim* | xray* | os68k* | v88r* \