* gash/lexer.scm (read-backquoted-command): Make the default procedure
accept a 'quoted?' keyword.
(get-backquoted-command): Accept a 'quoted?' keyword and pass it on to
'read-backquoted-command'.
(get-expansion): Accept a 'quoted?' keyword and pass it on to
'get-backquoted-command'.
(get-double-quotation): Set the 'quoted?' keyword when calling
'get-expansion'.
* tests/unit/lexer.scm: Add tests.
* gash/parser.scm (call-with-backquoted-input-port): Accept a
'quoted?' keyword which, if set, adds the double quote character to
the set of escapable characters.
(read-sh/backquoted): Accept a 'quoted?' keyword and pass it on to
'call-with-backquoted-input-port'.
* tests/unit/parser.scm: Add tests.
gash/environment.scm: Remove file.
geesh/*: Move these files into the 'gash' folder and replace all
instances of the word 'geesh'.
scripts/geesh.in: Remove file.
HACKING, INSTALL, Makefile.am, configure.ac, guix.scm,
tests/bootstrap/bash-without-bash.scm, tests/spec/Makefile.am,
tests/spec/check-spec, tests/spec/oil.scm, tests/unit/*,
tools/coverage.in: Replace all instances of the word 'geesh'.
Co-authored-by: Jan Nieuwenhuizen <janneke@gnu.org>