Bugfix to gregoriosyms.sty and gregoriotex-symbols.tex

The gregoriosyms style (which provides access to the special characters defined by gregoriotex without loading the score setting overhead) wasn't working as written.  The following changes have fixed that on my system:

1) gregoriotex-symbols.tex followed the OpenType Font loader code of luaotfload for naming the symbol font.  Thus, said package needs to be loaded in order for it to work.

2) gregoriotex-symbols.tex checks its version for compatibility with gregoriotex.  Since gregoriotex is not loaded when using gregoriosyms.sty, I needed to create a dummy command to bypass the version check.

3) Partial address of bug #21784 (https://gna.org/bugs/?21784).  This change makes it so that the symbol font is loaded at the default font size for the document.  The symbols, however, are still not responsive to size changes which are internal to the document (i.e. {\Huge \Vbar} and \Vbar produce the same thing).  Not sure how to address that without reloading the font each time a symbol is called for.
Revert "Bugfix to gregoriosyms.sty and gregoriotex-symbols.tex"

This reverts commit 0c92596a914054b9feee941a972af55e5b47b8d0.
Merge commit '04ddcea622e15f6a1e23b4b5ee94a813a8c4abec'

* commit '04ddcea622e15f6a1e23b4b5ee94a813a8c4abec':
  Bugfix to gregoriosyms.sty
Revert "Revert "Bugfix to gregoriosyms.sty and gregoriotex-symbols.tex""

This reverts commit b30e48a218d7e10563ed935ed82748962342b07f.