AIX 4.1 and 7.1RC2

To get 7.1RC2 to compile and pass the regression tests on AIX 4.1 I had to
make the following changes.

1) Makefile.global had the host_os and host_tuple full specified, but the
Makefile.port was expecting just aix4.1 instead of aix4.1.5.0

It looks like config/config.guess is using oslevel if it exists (which returns 4.1.5.0), but
otherwise will default to what uname gives (AIX apdev 1 4 006103684C00).

Not sure how to fix this permanently.

2) Makefile.shlib was missing the $LDFLAGS_SL to properly build shared libraries before
AIX 4.2. In Makefile.port its not defined, so should have no affect on AIX 4.2 and later.

Patch follows.

Thanks,
-rocco

*** Makefile.shlib.ORIG Mon Apr 2 12:58:28 2001
--- Makefile.shlib Mon Apr 2 12:59:33 2001
***************
*** 291,297 ****
# AIX case
$(shlib): lib$(NAME).a
$(MKLDEXPORT) lib$(NAME).a > lib$(NAME)$(EXPSUFF)
! $(COMPILER) -Wl,-H512 -Wl,-bM:SRE -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP) -Wl,-bE:lib$(NAME)$(EXPSUFF) -o $@ $< $(LDFLAGS) $(SHLIB_LINK)

endif # PORTNAME == aix

--- 291,297 ----
# AIX case
$(shlib): lib$(NAME).a
$(MKLDEXPORT) lib$(NAME).a > lib$(NAME)$(EXPSUFF)
! $(COMPILER) -Wl,-H512 -Wl,-bM:SRE -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP) -Wl,-bE:lib$(NAME)$(EXPSUFF) -o $@ $< $(LDFLAGS) $(SHLIB_LINK) -Wl,$(LDFLAGS_SL)

endif # PORTNAME == aix