Merge bitcoin-core/secp256k1#1384: build: enable ellswift module via SECP_CONFIG_DEFINES

78ca880 build: enable ellswift module via SECP_CONFIG_DEFINES (Jonas Nick)

Pull request description:

  ...like the other modules.

ACKs for top commit:
  sipa:
    utACK 78ca880
  real-or-random:
    utACK 78ca880

Tree-SHA512: c157a1ed912b9aa1a318aa0a70859a3ac67cb22303993f08ff00ed601e6ac197380dd503d3b361cbc4e698fc6489b5283b782f570f2703809d23668f3ebe5ba6

Author: real-or-random

configure.ac

@@ -401,7 +401,7 @@ if test x"$enable_module_schnorrsig" = x"yes"; then
 fi
 
 if test x"$enable_module_ellswift" = x"yes"; then
-  AC_DEFINE(ENABLE_MODULE_ELLSWIFT, 1, [Define this symbol to enable the ElligatorSwift module])
+  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_ELLSWIFT=1"
 fi
 
 # Test if extrakeys is set after the schnorrsig module to allow the schnorrsig