perldelta: update known problems
perldelta: Note patch fixed a bunch of tickets

Unbeknownst to the authors, several other tickets got fixed.
Add notice for removal of find2perl, s2p and a2p
Note that the minimum supported gcc (on Windows) is 3.4.5

Earlier versions (from www.mingw.org, at least) will build perl, but have
a linker bug that causes various tests to fail due to problems with
SDBM_File.dll. See perl #121936 for details.
Document known test failure in www.mingw.org builds of gcc-4.8.1 (at least)

This came up in perl #121643, but I forgot to add a note of this Known
Problem.
Update PathTools version in Porting
Remove note of test failures on FAT that were fixed by perl #21442's fixes

The list of tests fixed doesn't exactly match the list in README.win32, but
all tests now pass when building/testing on FAT with the Windows OS on NTFS.
Obituary for Greg McCarroll.