pcre: stub for pcre matchers

rm 3rd/sregex
add pcre content, rm sregex
3rd/pcre -b master
add lib/buffile (untested)
buffile: add testcase, fopen constructor also as method
use fmemopen only with linux
HAVE_FMEMOPEN (on darwin and mingw not)
fmemopen is no none BSD, so reverse the logic: linux and cygwin
allocate self freshly, do not use the stack variable

with tmpfile and fmemopen
gcc __attribute__ ((format (printf, i, j))) found a format problem

need to probe for it also
move libtommath to 3rd
pcre: stub for pcre matchers

rm 3rd/sregex
add potion_io_error, potion_type_error, can returns TRUE

write writes the binary ptr of more types
rm 3rd/sregex and dupl. 3rd/pcre
test requires now libs
Merge branch 'buffile' into p2

Fixed conflicts:
	.gitmodules
	3rd/libtommath
	core/potion.h