* mf/GNUmakefile: add '\' in multi-line "define ... endef"

* mf/GNUmakefile: add '\' in multi-line "define ... endef"
blocks (for make 3.80)

* scm/parser-ly-from-scheme.scm (ly:parse-string-result): add
\notemode so that user should not have to explicitely type it.

* scm/define-music-display-methods.scm: various
fixes (ApplyOutputEvent, ApplyContext; \new, \context and derived
constructs)

* input/no-notation/display-lily-tests.ly: new tests for
\applyOutput and \applyContext