Checks that the vala library in use is compatible with the given version.
This function is in the library, so it represents the vala library your code is running against.
| required_major |
the required major version |
| required_minor |
the required minor version |
| required_micro |
the required micro version |
|
null if the vala library is compatible with the given version, or a string describing the version mismatch. |