fix typo for vsnprintf in config.mk
diff --git a/config.mk b/config.mk
index 1b4479d..437c148 100644
--- a/config.mk
+++ b/config.mk
@@ -24,10 +24,10 @@
################################################################################
# Comment out the line below ('USE_SYS_DYN_MEM = yes'), or change it to
-# 'USE_SYS_DYN_MEM = no' if do NOT use malloc/calloc/realloc/free/vnsprintf()
+# 'USE_SYS_DYN_MEM = no' if do NOT use malloc/calloc/realloc/free/vsnprintf()
# provided by system for internal dynamic memory management.
#
-# NOTE: in that case, specify your own malloc/calloc/realloc/free/vnsprintf()
+# NOTE: in that case, specify your own malloc/calloc/realloc/free/vsnprintf()
# functions in your program via API cs_option(), using CS_OPT_MEM option type.
USE_SYS_DYN_MEM = yes