inconsistency with counting characters vs bytes for multi-byte characters

[Ed Morton]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: cygwin
Compiler: gcc
Compilation CFLAGS: -ggdb -O2 -pipe -Wall -Werror=format-security 
-Wp,-D_FORTIFY_SOURCE=2 -fstack-protector-strong 
--param=ssp-buffer-size=4 
-fdebug-prefix-map=/cygdrive/d/a/scallywag/gawk/gawk-5.2.2-1.x86_64/build=/usr/src/debug/gawk-5.2.2-1 
-fdebug-prefix-map=/cygdrive/d/a/scallywag/gawk/gawk-5.2.2-1.x86_64/src/gawk-5.2.2=/usr/src/debug/gawk-5.2.2-1 
-DNDEBUG
uname output: CYGWIN_NT-10.0-22621 TournaMart_2023 3.4.8-1.x86_64 
2023-08-17 17:02 UTC x86_64 Cygwin
Machine Type: x86_64-pc-cygwin

Gawk Version: 5.2.2

Attestation 1:
        I have read 
https://www.gnu.org/software/gawk/manual/html_node/Bugs.html.
        Yes

Attestation 2:
        I have not modified the sources before building gawk.
        True

Description:
        Different string handling functions produce different results 
for multi-byte characters.

Repeat-By:
        Without "-b":

        $ awk 'BEGIN{str="\342\200\257"; print length(str); 
match(str,/.+/); print RLENGTH; match(str,/$/); print RSTART }'
        1
        1
        4

        Note that length() thinks that string is 1 character, the first 
call to match() agrees, but then the 2nd call to match() thinks it's 3 
characters (since RSTART tells us the "end of string" is at position 4).

        Now with "-b" ("Cause gawk to treat all input data as 
single-byte characters" per 
https://www.gnu.org/software/gawk/manual/gawk.html#Options):

        $ awk -b 'BEGIN{str="\342\200\257"; print length(str); 
match(str,/.+/); print RLENGTH; match(str,/$/); print RSTART }'
        3
        3
        4

        Note that length() now thinks that string is 3 characters, the 
first call to match() agrees again, and then the 2nd call to match() now 
also agrees.

        Per the manual "in gawk, length(), substr(), split(), match() 
and the other string functions ... all work in terms of characters in 
the local character set, and not in terms of bytes." (from 
https://www.gnu.org/software/gawk/manual/html_node/Bytes-vs_002e-Characters.html) 
so I was expecting more consistent results between those 3 function 
calls and that they'd basically all always agree with length()s results. 
It may just be "match()" that has an issue, I haven't noticed a problem 
with any other function but I haven't been looking for it.