Allow +inv to work like -I

[jidanni]

This restriction makes zero sense.

: This works fine:
echo -88 42|proj \
+proj=pipeline \
+step +proj=utm +zone=16 \
+step +proj=utm +zone=16 +inv \
+step +proj=utm +zone=16
417181.93	4650259.85
: This also works fine:
echo -88 42|proj \
+proj=pipeline \
+step +proj=utm +zone=16 \
|proj +proj=utm +zone=16 -I
88dW	42dN
: So why not allow this to also work fine?:
echo -88 42|proj \
+proj=pipeline \
+step +proj=utm +zone=16 \
+step +proj=utm +zone=16 +inv
Rel. 9.3.1, December 1st, 2023
<proj>:
can't initialize operations that produce angular output coordinates
program abnormally terminated
: And indeed this should work too:
echo -88 42|proj \
+proj=pipeline \
+step +proj=utm +zone=16 \
|proj +proj=utm +zone=16 +inv
Rel. 9.3.1, December 1st, 2023
<proj>:
can't initialize operations that take non-angular input coordinates
program abnormally terminated

[rouault]

proj is a legacy utility that was designed to only deal with map projections, and that is now frozen.
If you use pipeline and +inv, you need to use cct instead.