[LyX/master] remove most traces of boost::regex

[Yuriy Skalko]

> In process of removing boost-traces from cmake-build, I got this error
> ...
> /usr2/src/lyx/lyx-git/src/support/checksum.cpp: In function ‘long unsigned int
> lyx::support::checksum(std::ifstream&)’: 
> /usr2/src/lyx/lyx-git/src/support/checksum.cpp:33:8:
> error: ‘for_each’ was not declared in this scope crc = for_each(beg, end, crc);
>         ^~~~~~~~
> /usr2/src/lyx/lyx-git/src/support/checksum.cpp:33:8: note: suggested 
> alternative: ‘fread’
>   crc = for_each(beg, end, crc);
>         ^~~~~~~~
> ...
> 
>         Kornel

Replacing "#include <iterator>" to "#include <algorithm>" should help.

Yuriy