Bogus Bison 3.8.2 warning: suspicious sequence in the output

Hi,

Bison 3.8.2 is issuing the following warning for a grammar whose 
semantic action includes the variable name my_charset_utf8mb4_bin:

yy_mariadb.cc:35834: warning: suspicious sequence in the output: b4_bin [-Wother]

It seems to me that the regular expression in 
http://git.savannah.gnu.org/cgit/bison.git/tree/src/scan-skel.l is too 
greedy, or the check should be suppressed if the input contains such 
identifiers.

A quick search of the Bison Texinfo for b4_ or m4_ did not find 
anything. Because those are not documented as reserved words or 
sequences, I think that identifiers like that should be allowed in 
semantic actions without Bison reporting any warnings.

With best regards,

	Marko