ENH: encapsulate wordRe regex with pointer

src/OSspecific/MSwindows/regExp/regExp.H

src/OSspecific/MSwindows/regExp/regExpFwd.H

src/OSspecific/POSIX/regExp/regExp.H

src/OSspecific/POSIX/regExp/regExpFwd.H

src/OSspecific/POSIX/regExp/regExpPosix.H

src/OpenFOAM/primitives/strings/regex/regExpCxx.H

src/OpenFOAM/primitives/strings/wordRe/wordRe.C

src/OpenFOAM/primitives/strings/wordRe/wordRe.H

src/OpenFOAM/primitives/strings/wordRe/wordReI.H