Remove Travis CI files

Obsoleted by GitHub Actions since #486

.travis-checkpatch.sh

@@ -1,45 +0,0 @@
-#!/bin/bash
-
-echo "Checking code style..."
-
-# Return failure as soon as a command fails to execute
-
-set -e
-
-# Download checkpatch.pl and related files
-
-echo "Getting checkpatch.pl..."
-
-mkdir checkpatchdir
-
-wget https://raw.githubusercontent.com/torvalds/linux/master/scripts/checkpatch.pl
-mv checkpatch.pl checkpatchdir/checkpatch.pl
-chmod +x checkpatchdir/checkpatch.pl
-
-touch checkpatchdir/const_structs.checkpatch
-touch checkpatchdir/spelling.txt
-
-# Run checkpatch.pl on the new commits
-
-echo "Running checkpatch.pl..."
-
-fname=$(mktemp)
-rc=0
-
-make CHECKPATCH=checkpatchdir/checkpatch.pl checkpatch > $fname
-
-cat $fname
-
-if grep "ERROR" $fname; then
-    # At least one error found
-    echo "Code style errors have been found!"
-    rc=1
-else
-    echo "No code style errors found, your patches are ready!"
-fi
-
-# Cleanup
-
-rm -rf checkpatchdir
-
-exit $rc

.travis-deps.sh

@@ -1,13 +0,0 @@
-#!/bin/sh
-
-if [ $TRAVIS_OS_NAME = "osx" ]; then
-    brew update
-    brew install libpng pkg-config md5sha1sum
-else # linux
-    sudo apt-get -qq update
-    sudo apt-get install -y -q bison flex libpng-dev pkg-config
-fi
-
-echo "Dependencies:"
-yacc --version
-flex --version

.travis.yml

@@ -1,19 +0,0 @@
-language: c
-sudo: required
-install:
-  - ./.travis-deps.sh
-  - make Q=
-  - sudo make install Q=
-os:
-  - linux
-  - osx
-compiler:
-  - clang
-  - gcc
-script:
-  - cd test && ./run-tests.sh
-matrix:
-  include:
-    - env: _="checkpatch"
-      script:
-        - ./.travis-checkpatch.sh