Further fix install program detection

The $(or) make function was introduced in GNU make 3.81, so the
previous coding didn't work in 3.80.  Write it differently, and
improve the variable naming to make more sense in the new coding.

configure

@@ -693,7 +693,7 @@ MKDIR_P
 AWK
 LN_S
 TAR
-INSTALL_
+install_bin
 INSTALL_DATA
 INSTALL_SCRIPT
 INSTALL_PROGRAM
@@ -6956,8 +6956,8 @@ test -z "$INSTALL_DATA" && INSTALL_DATA='${INSTALL} -m 644'
 # a relative path to it in each makefile where it subsitutes it. This clashes
 # with our Makefile.global concept. This workaround helps.
 case $INSTALL in
-  *install-sh*) INSTALL_='';;
-  *) INSTALL_=$INSTALL;;
+  *install-sh*) install_bin='';;
+  *) install_bin=$INSTALL;;
 esac

configure.in

@@ -814,10 +814,10 @@ AC_PROG_INSTALL
 # a relative path to it in each makefile where it subsitutes it. This clashes
 # with our Makefile.global concept. This workaround helps.
 case $INSTALL in
-  *install-sh*) INSTALL_='';;
-  *) INSTALL_=$INSTALL;;
+  *install-sh*) install_bin='';;
+  *) install_bin=$INSTALL;;
 esac
-AC_SUBST(INSTALL_)
+AC_SUBST(install_bin)
 
 AC_PATH_PROG(TAR, tar)
 AC_PROG_LN_S

src/Makefile.global.in

@@ -289,8 +289,9 @@ BZIP2	= bzip2
 
 # Installation.
 
+install_bin = @install_bin@
 install_sh = $(SHELL) $(top_srcdir)/config/install-sh -c
-INSTALL = $(if $(use_install_sh),$(install_sh),$(or @INSTALL_@,$(install_sh)))
+INSTALL = $(if $(use_install_sh),$(install_sh),$(if $(install_bin),$(install_bin),$(install_sh)))
 
 INSTALL_SCRIPT_MODE	= 755
 INSTALL_DATA_MODE	= 644