Fixes in the configury logic

[artpol84]

• Rename configure.in to configure.ac as autoreconf suggests
• Switch from the custom-modified configure/mpiPconfig.h.in to
  the auto-generated by autoreconf
• Modify few config vars to prepare to get rid of mpiPi.h.in

Signed-off-by: Artem Polyakov artpol84@gmail.com

[artpol84]

@cchambreau I believe this is a cleaner solution to the problem in #12

[artpol84]

P.S.

• Optionally, we can keep or get rid of configure + mpiPconfig.h.in's and always autogenerate them as OMPI package does for example.
  This will require autotools to be installed on the machine. However, those who get the git version are developers and expected to have these tools.
  Up to you.
• This needs to be checked against a variety of building options. I've only covered the following configure line so far:

./configure --prefix=`pwd`/install \
	--with-binutils-dir=/home/artpol/sandbox/binutils-2.32/ \
	--with-libunwind=/home/artpol/sandbox/libunwind-1.3.1/ \
	--with-cc=/home/artpol/sandbox/openmpi-3.1.3/bin/mpicc \
	--without-f77 --enable-demangling=GNU \
	CFLAGS="-g -O0" --enable-stackdepth=15

[artpol84]

I also suggest moving from Makefile.in to Makefile.am to have a clean solution.