a.* in autoconf 2.50 configure script

[Bill Schottstaedt]

If the directory where an autoconf 2.50 configure script is run
has a pre-exisiting file with a name like a.ins, the script gets
confused about compiler extensions:

/home/bil/cl/ ./configure
checking build system type... i686-pc-linux-gnu
checking host system type... i686-pc-linux-gnu
checking for gcc... gcc
checking for C compiler default output... a.ins
checking whether the C compiler works... configure: error: cannot run C 
compiled programs.
If you meant to cross compile, use `--host'.
/home/bil/cl/ ls -la a.ins
-rw-r--r--    1 bil      bil          5795 Jul 24  1999 a.ins