Workaround for infinite recursion crash

* FreeBSD crashes on infinite recursion rather than throwing a stack
  overflow because the stack address of the fault is in the page below
  the guard area.  Workaround this by rounding down the fault address to
  the nearest page boundary.  Investigation is still under way into what
  may be causing this but this appears to prevent it in simple test cases.

PR:		222146

java/openjdk8/Makefile

@@ -2,6 +2,7 @@
 
 PORTNAME=	openjdk
 PORTVERSION=	${JDK_MAJOR_VERSION}.${JDK_UPDATE_VERSION}.${JDK_BUILD_NUMBER:S/^0//}.${BSD_JDK_VERSION}
+PORTREVISION=	1
 CATEGORIES=	java devel
 MASTER_SITES=	LOCAL/jkim:jtreg
 PKGNAMESUFFIX?=	${JDK_MAJOR_VERSION}

java/openjdk8/files/patch-hotspot_src_os__cpu_bsd__x86_vm_os__bsd__x86.cpp

@@ -0,0 +1,12 @@
+--- hotspot/src/os_cpu/bsd_x86/vm/os_bsd_x86.cpp.orig	2019-08-11 09:24:22.211149000 -0700
++++ hotspot/src/os_cpu/bsd_x86/vm/os_bsd_x86.cpp	2019-08-11 09:25:08.826582000 -0700
+@@ -470,6 +470,9 @@
+     // Handle ALL stack overflow variations here
+     if (sig == SIGSEGV || sig == SIGBUS) {
+       address addr = (address) info->si_addr;
++#ifdef __FreeBSD__
++      addr = (unsigned char*) align_ptr_down(addr, os::vm_page_size());
++#endif
+ 
+       // check if fault address is within thread stack
+       if (addr < thread->stack_base() &&