Fix various compatibility problems with newer GCC.

This is an amalgamation of these upstream commits:

  https://git.savannah.gnu.org/cgit/src-highlite.git/commit/?id=904949c9026cb772dc93fbe0947a252ef47127f4
  https://git.savannah.gnu.org/cgit/src-highlite.git/commit/?id=ab9fe5cb9b85c5afab94f2a7f4b6d7d473c14ee9

diff --git a/lib/srchilite/fileutil.cc b/lib/srchilite/fileutil.cc
index 59a6d64..963178c 100644
--- a/lib/srchilite/fileutil.cc
+++ b/lib/srchilite/fileutil.cc
@@ -48,7 +48,7 @@ void set_file_util_verbose(bool b) {
 // FIXME avoid using a global variable
 std::string start_path;
 
-string readFile(const string &fileName) throw (IOException) {
+string readFile(const string &fileName) {
     ifstream file(fileName.c_str());
 
     if (!file.is_open()) {
diff --git a/lib/srchilite/fileutil.h b/lib/srchilite/fileutil.h
index 7335a9b..042eb56 100644
--- a/lib/srchilite/fileutil.h
+++ b/lib/srchilite/fileutil.h
@@ -27,7 +27,7 @@ extern std::string start_path;
  * @return the contents of the file
  * @throw IOException
  */
-string readFile(const string &fileName) throw (IOException);
+string readFile(const string &fileName);
 
 //char *read_file(const string &fileName);
 
diff --git a/lib/tests/stdboosterror.h b/lib/tests/stdboosterror.h
index 568545b..d59bfa6 100644
--- a/lib/tests/stdboosterror.h
+++ b/lib/tests/stdboosterror.h
@@ -4,7 +4,7 @@
 #include <boost/regex/pattern_except.hpp>
 
 static boost::regex_error
-        std_boost_exception(boost::regex_error(boost::regex_constants::error_bad_pattern));
+        std_boost_exception = boost::regex_error(boost::regex_constants::error_bad_pattern);
 
 /**
  * returns the string representing a standard exception (which
diff --git a/lib/tests/test_wordtokenizer_main.cpp b/lib/tests/test_wordtokenizer_main.cpp
index 40e23b1..11ba389 100644
--- a/lib/tests/test_wordtokenizer_main.cpp
+++ b/lib/tests/test_wordtokenizer_main.cpp
@@ -11,6 +11,14 @@
 using namespace std;
 using namespace srchilite;
 
+/*
+ * We have to use 'std' namespaces because 'WordTokenizer::WordTokenizerResults::value_type'
+ * is an std::pair<std::string, std::string> in disguise. We have to place 'operator<<()'
+ * into the same namespace for ADL to work. Otherwise gcc-12 or clang-13 can't find the
+ * overload.
+ */
+namespace std {
+
 static ostream &operator <<(ostream &os, const WordTokenizer::WordTokenizerResults::value_type &);
 
 ostream &operator <<(ostream &os, const WordTokenizer::WordTokenizerResults::value_type &token) {
@@ -23,6 +31,8 @@ ostream &operator <<(ostream &os, const WordTokenizer::WordTokenizerResults::val
     return os;
 }
 
+}
+
 int main() {
     WordTokenizer::WordTokenizerResults tokens;