Modernize examples/hello_cxxlib with DPxxx variables
Convert almost all examples to LIBDEPS from linkme.mk
LDCOMPILER variable was removed.
Compiler is always used for linking.
mkc_imp.foreign_autotools.mk: ${.CURDIR}/compile is also removed by target "cleandir"
add helpers/mkc_long_lines
New builtin: prog_gmake
Enable examples/hello_require_tools by default
mkc_imp.foreign_autotools.mk: if AT_USE_AUTOMAKE==yes, we MKC_REQUIRE_PROGS+=automake
Forgot to add custom/prog_gmake
One more project examples/hello_autoconf for autotools support
helpers/mkc_long_lines was commited by mistake