Improve the error message for loading an old version of the GMT library

[seisman]

Description of proposed changes

See the forum post for context.

When multiple GMT versions are installed, PyGMT may incorrectly load the old version (e.g., GMT 5.4.5) and reports that it can't access a function GMT_xxx. As shown in the forum post, the error message is not helpful at all.

In this PR, we improve the error message:

1. Show the library name libgmt._name (name or full path, depending on how the library was loaded) in the error message
2. Mention that the possible cause is PyGMT is loading an old version of the GMT library

Now the error message is:

GMTCLibError: Error loading '/path/to/libgmt.so'. Couldn't access function GMT_Create_Session. Maybe loading an old version of the GMT shared library.

The test test_check_libgmt is also updated to check the improve message.

Fixes #

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash commands are:

• /format: automatically format and lint the code
• /test-gmt-dev: run full tests on the latest GMT development version

[seisman]

/test-gmt-dev