Use oif_interface_ prefix for C implementations

[dmitry-kabanov]

Issue description:
There is a lack of "namespacing" in C implementations right now: precisely, functions are called the same way as they called, e. g., in Python. It would be better if all functions have prefixes oif_interface_ so that it would be clear in the implementation, which functions implement a given interface.

Also, on the implementation side the interfaces have this prefix, therefore, their inclusion into implementations is useless as then C compiler does not check conformance, actually.

TODOS:

• Modify dispatch_c module so that each function invocation of a C implementation contains prefix oif_interface_ prepended to the method name passed as an argument to call_impl_method
• Probably, C implementations should carry with them the information about what interface they implement: that is, interface name must be copied during implementation initialization
• Modify existing C implementations such as c_qeq, c_lapack, and sundials_cvode so that the function names have this prefix