bug#25647: grep 2.28 fails to build on CentOS 6

[Zube]

  CC       pcresearch.o
pcresearch.c:53: error: expected specifier-qualifier-list before 
'pcre_jit_stack'
gmake[2]: *** [Makefile:1363: pcresearch.o] Error 1
gmake[2]: Leaving directory '/stat/src/grep/grep-2.28/src'
gmake[1]: *** [Makefile:1291: all-recursive] Error 1
gmake[1]: Leaving directory '/stat/src/grep/grep-2.28'
gmake: *** [Makefile:1232: all] Error 2

possibly due the age of the native pcre:

pcre-7.8-7.el6.x86_64

On CentOS 7 with:

pcre-8.32-15.el7_2.1.x86_64

it builds fine.  Also builds fine on CentOS 6 with --disable-perl-regexp.

Cheers,
Zube