Update obsolete Autotools macros

[pragnyanramtha]

Fixes #11

Summary

• Replace obsolete Autotools macros in configure.ac with current equivalents.
• Replace obsolete AC_TRY_LINK checks in the local MPI detection macro with AC_LINK_IFELSE.
• Keep the change limited to existing Autotools input files.

Root cause

The build configuration still used macros that modern Autoconf reports as obsolete, including AM_CONFIG_HEADER, AC_AIX, AC_LANG_CPLUSPLUS, AC_PROG_LIBTOOL, and AC_TRY_LINK.

Files changed

• acinclude.m4
• configure.ac

Tests run

• git diff --check
• autoreconf -fi -W obsolete,error in a throwaway copy
• ./configure --without-python in a throwaway copy
• make -j2 in a throwaway copy

Risk

Low. The updates use Autoupdate-recommended macro replacements and preserve the same MPI link-test logic.

[Copilot]

Pull request overview

This PR modernizes obsolete Autotools macros to resolve issue #11 while preserving the existing build configuration behavior.

Changes:

• Replaces deprecated Autoconf/Automake macros in configure.ac with current equivalents.
• Converts MPI link checks in acinclude.m4 from AC_TRY_LINK to AC_LINK_IFELSE.
• Keeps updates limited to Autotools input files.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
configure.ac	Updates obsolete Autotools macros and removes redundant libtool initialization.
acinclude.m4	Modernizes MPI link-test macros without changing detection logic.

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