Add --cover option to ./configure for gcc coverage testing.

This adds the -fprofile-arcs and -ftest-coverage options when compiling
the source code for the static library.  Those same options must then be
used when linking the static library into an executable.  This updates
Makefile.in to remove and .gitignore to ignore the files generated when
testing coverage.

.gitignore

@@ -9,6 +9,10 @@
 *.o
 *.dylib
 
+*.gcda
+*.gcno
+*.gcov
+
 /example
 /example64
 /examplesh

Makefile.in

@@ -232,6 +232,7 @@ clean:
 	   libz.* foo.gz so_locations \
 	   _match.s maketree contrib/infback9/*.o
 	rm -rf objs
+	rm -f *.gcda *.gcno *.gcov
 
 maintainer-clean: distclean
 distclean: clean zconf zconf.h.cmakein docs

configure

@@ -55,6 +55,7 @@ mandir=${mandir-'${prefix}/share/man'}
 shared_ext='.so'
 shared=1
 solo=0
+cover=0
 zprefix=0
 build64=0
 gcc=0
@@ -85,6 +86,7 @@ case "$1" in
     -s* | --shared | --enable-shared) shared=1; shift ;;
     -t | --static) shared=0; shift ;;
     --solo) solo=1; shift ;;
+    --cover) cover=1; shift ;;
     -z* | --zprefix) zprefix=1; shift ;;
     -6* | --64) build64=1; shift ;;
     -a*=* | --archs=*) ARCHS=`echo $1 | sed 's/.*=//'`; shift ;;
@@ -345,6 +347,10 @@ OBJC='$(OBJZ)'
 PIC_OBJC='$(PIC_OBJZ)'
 fi
 
+if test $cover -eq 1; then
+  CFLAGS="${CFLAGS} -fprofile-arcs -ftest-coverage"
+fi
+
 cat > $test.c <<EOF
 #include <stdio.h>
 #include <stdarg.h>
@@ -578,7 +584,7 @@ case $CFLAGS in
     fi ;;
 esac
 
-rm -f $test.[co] $test $test$shared_ext
+rm -f $test.[co] $test $test$shared_ext $test.gcno
 
 # udpate Makefile
 sed < Makefile.in "