Add a ./config --solo option to make zlib subset with no libary use

A common request has been the ability to compile zlib to require no
other libraries.  This --solo option provides that ability.  The price
is that the gz*, compress*, and uncompress functions are eliminated,
and that the user must provide memory allocation and free routines to
deflate and inflate when initializing.

configure

@@ -54,11 +54,14 @@ includedir=${includedir-'${prefix}/include'}
 mandir=${mandir-'${prefix}/share/man'}
 shared_ext='.so'
 shared=1
+solo=0
 zprefix=0
 build64=0
 gcc=0
 old_cc="$CC"
 old_cflags="$CFLAGS"
+OBJC='$(OBJZ) $(OBJG)'
+PIC_OBJC='$(PIC_OBJZ) $(PIC_OBJG)'
 
 while test $# -ge 1
 do
@@ -81,6 +84,7 @@ case "$1" in
     -i* | --includedir) includedir="$2"; shift; shift ;;
     -s* | --shared | --enable-shared) shared=1; shift ;;
     -t | --static) shared=0; shift ;;
+    --solo) solo=1; shift ;;
     -z* | --zprefix) zprefix=1; shift ;;
     -6* | --64) build64=1; shift ;;
     -a*=* | --archs=*) ARCHS=`echo $1 | sed 's/.*=//'`; shift ;;
@@ -331,6 +335,16 @@ if test $zprefix -eq 1; then
   echo "Using z_ prefix on all symbols."
 fi
 
+if test $solo -eq 1; then
+  sed '/#define ZCONF_H/a\
+#define Z_SOLO
+
+' < zconf.h > zconf.temp.h
+  mv zconf.temp.h zconf.h
+OBJC='$(OBJZ)'
+PIC_OBJC='$(PIC_OBJZ)'
+fi
+
 cat > $test.c <<EOF
 #include <stdio.h>
 #include <stdarg.h>
@@ -589,6 +603,8 @@ sed < Makefile.in "
 /^sharedlibdir *=/s#=.*#=$sharedlibdir#
 /^includedir *=/s#=.*#=$includedir#
 /^mandir *=/s#=.*#=$mandir#
+/^OBJC *=/s#=.*#= $OBJC#
+/^PIC_OBJC *=/s#=.*#= $PIC_OBJC#
 /^all: */s#:.*#: $ALL#
 /^test: */s#:.*#: $TEST#
 " > Makefile