Fix tests with GNU grep 3.8

GNU grep 3.8 started to emit warnings when invoking egrep.
Convert all calls to grep -E.

abi-perf-test

@@ -3,7 +3,7 @@ set -eo pipefail
 cd $(dirname $0)
 whoami=$(basename $0)
 
-if [[ $(git status -s | egrep -v abi-perf-test | wc -l) != 0 ]]; then
+if [[ $(git status -s | grep -E -v abi-perf-test | wc -l) != 0 ]]; then
     echo 1>&2 "${whoami}: git is not clean. (abi-perf-test changes ignored)"
     git status -s
     exit 2

build-scripts/build-doc

@@ -10,7 +10,7 @@ pip3 install sphinx sphinx_rtd_theme
 cmake -S . -B build -DBUILD_DOC=1
 cmake --build build --target doc_dist
 zip -r doc.zip build/manual/doc-dist
-version=$(egrep '^release' manual/conf.py | cut -d"'" -f 2)
+version=$(grep -E '^release' manual/conf.py | cut -d"'" -f 2)
 mv build/manual/doc-dist qpdf-${version}-doc
 mkdir distribution
 zip -r distribution/qpdf-${version}-doc-ci.zip qpdf-${version}-doc

build-scripts/build-fuzzer

@@ -8,7 +8,7 @@ sudo apt-get -y install build-essential cmake zlib1g-dev libjpeg-dev
 ./fuzz/oss-fuzz-build
 ls -l out/qpdf_fuzzer
 ls -l out/
-if ldd out/qpdf_fuzzer | egrep 'libjpeg|libz|libqpdf'; then
+if ldd out/qpdf_fuzzer | grep -E 'libjpeg|libz|libqpdf'; then
     echo 1>&2 "*** Fuzzers linked dynamically with some dependent libraries."
     ldd out/qpdf_fuzzer
     exit 2

qpdf/qtest/qpdf/diff-encrypted

@@ -1,5 +1,5 @@
 #!/bin/sh
-lines=$(expr 0 + $(diff "$1" "$2" | egrep '^[<>]' | egrep -v '(Date|InstanceID)' | wc -l))
+lines=$(expr 0 + $(diff "$1" "$2" | grep -E '^[<>]' | grep -E -v '(Date|InstanceID)' | wc -l))
 if [ "$lines" = "0" ]; then
    echo okay
 else

qpdf/qtest/qpdf/diff-ignore-ID-version

@@ -1,6 +1,6 @@
 #!/bin/sh
-lines=$(expr 0 + $(diff "$1" "$2" | egrep '^[<>]' | \
+lines=$(expr 0 + $(diff "$1" "$2" | grep -E '^[<>]' | \
-        egrep -v '/ID' | egrep -v '%PDF-' | wc -l))
+        grep -E -v '/ID' | grep -E -v '%PDF-' | wc -l))
 if [ "$lines" = "0" ]; then
    echo okay
 else