unbreak net-im/uTox on 10.3-RELEASE amd64

[ 83%] Building C object CMakeFiles/utox.dir/src/main.c.o
/usr/bin/cc -I/usr/local/include/freetype2 -O2 -pipe -fstack-protector -isystem /usr/local/include -fno-strict-aliasing -Wall -Wextra -fno-strict-aliasing -O2 -pipe -fstack-protector -isystem /usr/local/include -fno-strict-aliasing -std=gnu99 -o CMakeFiles/utox.dir/src/main.c.o -c /wrkdirs/usr/ports/net-im/uTox/work/uTox-1835eae/src/main.c
In file included from /wrkdirs/usr/ports/net-im/uTox/work/uTox-1835eae/src/main.c:5:
In file included from /wrkdirs/usr/ports/net-im/uTox/work/uTox-1835eae/src/main.h:282:
In file included from /wrkdirs/usr/ports/net-im/uTox/work/uTox-1835eae/src/stb_image.h:678:
/usr/include/clang/3.4.1/emmintrin.h:1444:21: error: expected '(' after 'asm'

__asm__ volatile ("pause");
                  ^

/wrkdirs/usr/ports/net-im/uTox/work/uTox-1835eae/src/main.h:84:21: note: expanded from macro 'volatile'
#define volatile(x) x

^

PR: 216332
Submitted by: cpm, amdmi3
Reviewed by: matthew
Approved by: matthew (mentor), portmaster@BSDforge.com (maintainer timeout, 2 weeks)
Differential Revision: https://reviews.freebsd.org/D9477