A few typos in gcc/testsuite/gfortran.dg

[FX Coudert]

Thanks Dominique for the notice, I committed your fixes as rev.  
127001, after regtesting on x86_64-linux.

Three of these testcases were written by Daniel; another one was part  
of the ISO_C_BINDING merge. As a general reminder to all of us (me  
included), the syntax is { dg-do XXXX } where XXX can be compile,  
assemble, link or run; also note that the spaces inside the { curly  
brackets } are needed.

FX, back from holidays