Support writing PE32/PE32+ section permissions

[yol]

Hi,

I'm working on adding support for writing PE32(+) section permissions (see #921).

The patch works fine so far (it's mostly adapted from the ELF code), but I've seen that sections that do not have a name get one auto-assigned. bins/pe/normal64.exe is an example of this:

[Sections]
idx=00 vaddr=0x00401000 paddr=0x00000200 sz=512 vsz=4096 perm=m--wx name=sect_0

Here sect_0 was autogenerated and is not actually in the file. This is a problem when trying to modify the section permissions, as the code checks the raw names from the binary and not the ones radare "sees". So to change the permissions one would have to invoke rabin2 like this: rabin2 -O p//x normal64.exe (i.e. with empty section name). It works, but it's not pretty and also fails when there are multiple unnamed sections. How could this be handled better? I can't use the parsed section info for looking up the name since that can't be mapped back to the right section in the binary (sections might get dropped during parsing under certain circumstances so the indices could differ).

[Maijin]

Can you make a PR for test here https://github.com/radare/radare2-regressions/tree/master/t.tools/rabin2 ?

[yol]

Done