patch 8.0.0445: getpgid is not supported on all systems

Problem:    Getpgid is not supported on all systems.
Solution:   Add a configure check.
diff --git a/src/configure.ac b/src/configure.ac
index 113fad1..4445cf5 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -3609,7 +3609,7 @@
 AC_CHECK_FUNCS(fchdir fchown fsync getcwd getpseudotty \
 	getpwent getpwnam getpwuid getrlimit gettimeofday getwd lstat \
 	memset mkdtemp nanosleep opendir putenv qsort readlink select setenv \
-	setpgid setsid sigaltstack sigstack sigset sigsetjmp sigaction \
+	getpgid setpgid setsid sigaltstack sigstack sigset sigsetjmp sigaction \
 	sigprocmask sigvec strcasecmp strerror strftime stricmp strncasecmp \
 	strnicmp strpbrk strtol tgetent towlower towupper iswupper \
 	usleep utime utimes)