Silence MSVC warning about non-void prototypes

It thinks that these functions don't match the function pointer type
that they are passed with:

GCDAProfiling.c(578) : warning C4113: 'void (__cdecl *)()' differs in parameter lists from 'void (__cdecl *)(void)'
GCDAProfiling.c(579) : warning C4113: 'void (__cdecl *)()' differs in parameter lists from 'void (__cdecl *)(void)'
GCDAProfiling.c(580) : warning C4113: 'void (__cdecl *)()' differs in parameter lists from 'void (__cdecl *)(void)'

llvm-svn: 260475