I happened to notice that MODIFY_JNI_METHOD_CALL was defined in
cygming.h and documented in tm.texi.  However, because it was only
needed for gcj, it is obsolete.  This patch removes the vestiges.

Tested by grep, and rebuilding the documentation.

gcc/ChangeLog
2019-11-18  Tom Tromey  <tromey@adacore.com>

	* doc/tm.texi: Rebuild.
	* doc/tm.texi.in (Misc): Don't document MODIFY_JNI_METHOD_CALL.
	* config/i386/cygming.h (MODIFY_JNI_METHOD_CALL): Don't define.

From-SVN: r278407