Improper substitution of @srcdir@ in VPATH template for "in-source" configure

[Keith Marshall]

Initially reported here:
http://thread.gmane.org/gmane.comp.gnu.mingw.user/33435/focus=33455

Reproduced with:
  autoconf-2.61 on MSYS/Win2K
  autoconf-2.63 on Ubuntu-8.04-LTS

Minimal test case:

  $ cat Makefile.in
  # @configure_input@
  srcdir = @srcdir@
  VPATH = @srcdir@/src
  # EOF

  $ cat configure.ac
  AC_INIT
  AC_CONFIG_FILES([Makefile])
  AC_OUTPUT
  # EOF

  $ autoconf

  $ ./configure

  $ grep VPATH Makefile
  VPATH = /src

Note that this should be `VPATH = ./src', but the dot, which should 
have resulted from substitution of @srcdir@, has been elided.  Note 
however:

  $ mkdir bld ; cd bld

  $ ../configure

  $ grep VPATH Makefile
  VPATH = ../src

yields the expected result.

-- 
Regards,
Keith.