cobol: Allow for undefined NAME_MAX [PR119217]

cobol: Allow for undefined NAME_MAX [PR119217]

All users of symbols.h fail to compile on Solaris:

/vol/gcc/src/hg/master/local/gcc/cobol/symbols.h: At global scope:
/vol/gcc/src/hg/master/local/gcc/cobol/symbols.h:1365:13: error: ‘NAME_MAX’ was not declared in this scope
 1365 |   char name[NAME_MAX];
      |             ^~~~~~~~

NAME_MAX being undefined is allowed by POSIX.1, actually: it's listed
for <limits.h> under "Pathname Variable Values":

A definition of one of the symbolic constants in the following list
shall be omitted from the <limits.h> header on specific implementations
where the corresponding value is equal to or greater than the stated
minimum, but where the value can vary depending on the file to which it
is applied. The actual value supported for a specific pathname shall be
provided by the pathconf() function.

As a hack, this patch provides a fallback definition to allow the build
to finish.   In fact it turned out that cbl_funtion_t.name isn't filename
related and never set at all, so this patch serves as a mere stopgap fix
to unbreak the build until a real solution can be figured out.

Bootstrapped without regressions on amd64-pc-solaris2.11,
sparcv9-sun-solaris2.11, and x86_64-pc-linux-gnu.

2025-04-08  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	gcc/cobol:
	PR cobol/119217
	* symbols.h (NAME_MAX): Define fallback.