configure: check whether shell is capable of parameter substring processing

configure: check whether shell is capable of parameter substring processing

'configure' script uses parameter substring extensively. It is Posix shell
feature. Original Bourne shell does not have such features. Some systems
still ships such shells as /bin/sh (for compatibility reasons -- shell
scripts written on those platforms are expected to work on 1990's systems).

Just testing whether parameter substring processing works will make the
shell exit due to syntax error if it is not compatible. Therefore the test
is executed in a subshell -- subshell exits with nonzero value when the
operation in question fails.

As 'if ! ...' does not work in Bourne shell, Short-circuiting construct
'||' is used to print information message and exit when expected.