lang/execline: 2.1.3.1 -> 2.1.4.2

• New EXECLINE_BLOCK_END_STRING and EXECLINE_BLOCK_QUOTE_STRING macros
• New command: withstdinas. It's a simplification of backtick, which is now implemented as a combination of pipeline and withstdinas.
• Other new command: getcwd.

PR: 203789
Submitted by: Colin Booth <colin@heliocat.net> (maintainer)