Use module 'c99' when needed for variadic macros with '...' syntax

[Bruno Haible]

When compiling a gnulib testdir with CC="gcc -std=gnu90 -pedantic" (without
the 'c99' module) I see these warnings:

./malloc/scratch_buffer.h:107:55: warning: ISO C99 requires at least one 
argument for the "..." in a variadic macro
./malloc/scratch_buffer.h:124:56: warning: ISO C99 requires at least one 
argument for the "..." in a variadic macro
./malloc/scratch_buffer.h:95:46: warning: ISO C99 requires at least one 
argument for the "..." in a variadic macro
sm3.c:409:48: warning: ISO C99 requires at least one argument for the "..." in 
a variadic macro

Thus, the modules 'scratch_buffer' and 'crypto/sm3' are effectively already
using C11. C90 compilers surely will reject this syntax.


2020-09-05  Bruno Haible  <bruno@clisp.org>

        Use module 'c99' when needed for variadic macros with '...' syntax.
        * modules/crypto/sm3 (Depends-on): Add c99.

diff --git a/modules/crypto/sm3 b/modules/crypto/sm3
index 007fbc4..3df7d88 100644
--- a/modules/crypto/sm3
+++ b/modules/crypto/sm3
@@ -8,6 +8,7 @@ m4/sm3.m4
 
 Depends-on:
 byteswap
+c99
 extern-inline
 stdalign
 stdint