Add clang support to definition of METHCLA_VISIBLE
Rename sine.cpp to sine.c
Restructure static loader mechanism

Resolve symbols with a prefix from the application binary. Uses an informal symbolPrefix RDF predicate and depends on the symbols being resolved at runtime to be listed in a file passed to the `-exported-symbols-list linker` option (otherwise they are stripped from the executable).
Factor common definitions into common.h
Include lv2.h
Wrap license header in C comments
Simplify interface for static library plugin functions
Make freeing request payload caller's responsibility

The original request payload is passed to the response callback and the caller is expected to clean up any resources within the callback.
Implement methcla_engine_request
Return nullptr for out of bound resource ids
Initialize connection bus id with invalid id
Whitespace fixes
Add C++ LV2 atom forge wrapper
Fix comment spelling
Implement Insert API request for instantiating synths
Add beginnings of C++ engine API