Move the declaration of query_config() to a dedicated header file

Declaring query_config() belongs with the query_config program, not in
ssl_test_lib.h, so move the declaration to a new header file
query_config.h.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/programs/test/query_config.c b/programs/test/query_config.c
index 1345b11..d15c7e9 100644
--- a/programs/test/query_config.c
+++ b/programs/test/query_config.c
@@ -23,6 +23,8 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 
+#include "query_config.h"
+
 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else