Prefer $(info) to @echo

Prefer $(info) to @echo

Have GNU Make output some diagnostics directly, instead of forking
and execing a shell to do it.
* GNUmakefile (help):
* doc/lispref/two-volume.make (vol2.pdf, elisp2med-init)
(elisp2-init):
* doc/misc/Makefile.in (echo-info, echo-sources):
* lib-src/Makefile.in (archlibdir, install, check):
* src/verbose.mk.in (AM_V_AR, AM_V_CC, AM_V_CXX, AM_V_CCLD)
(AM_V_CXXLD, AM_V_ELC, AM_V_ELN, AM_V_GEN, AM_V_GLOBALS)
(AM_V_RC):
* test/Makefile.in (subdirs, subdir-targets):
Prefer $(info) to @echo.
* GNUmakefile (MAKECMDGOALS, configure, Makefile):
Prefer $(warning) to @echo >&2.
* src/verbose.mk.in (AM_V_ELN): Output target, like the others.