New environment variable TLS_INTERPOSER_DH_PEM_FILE to load a custom DH parameters PEM file.
A 2048 bit long DH parameters file can be generated with:
	openssl dhparam -out dh2048.pem 2048

Based on code by Erwann Abalea: https://issues.apache.org/bugzilla/show_bug.cgi?id=49559