[goroyabu]

Summary

• bump the repository package version from 0.4.0 to 0.5.0
• align generated CMake and pkg-config package metadata with the planned
  v0.5.0 release tag

Related Issue

Closes #73

Verification

• strict offline configure and build completed successfully using the pinned
  local upstream archives
• full local test suite passed: 68/68 tests
• staged installation completed successfully
• installed CMake consumer example passed: 2/2 tests
• installed f2cConfig.cmake reports F2C_VERSION_STRING as 0.5.0
• installed libf2c.pc reports Version: 0.5.0
• git diff --check passed

Impact

This prepares the next minor source release. There are no additional API,
installation-layout, or compatibility changes beyond the accumulated changes
already merged since v0.4.0.

Documentation

No documentation changes. Existing version references outside the root project
declaration are illustrative examples rather than the current package version.

Checklist

• The change is focused on one coherent maintenance outcome.
• Relevant local verification has been run and reported above.
• User-facing workflows and supported behavior are documented when changed.
• No downloaded upstream archives, extracted vendor sources, build outputs,
  or generated files were committed unintentionally.