RISC-V glibc port, v6

[Joseph Myers]

Version 6 is OK to commit with the fixes noted in the review, provided the 
committed version builds and builds tests (for each of the supported 
configurations) without --disable-werror and has at most 20 
architecture-specific failures in each of those configurations.

The fixes noted in the review are, again:

* crti.S should follow pt-crti.S exactly for .section directive.

* Remove the <sys/asm.h> include in crti.S.

* Use #ifndef in math-tests.h, twice.

* Fix off-by-one errors in add_system_dir.

* Remove stray 32-bit ABI references in patch 15.

Note the following wiki updates required for adding a new port.

* Add yourself as maintainer in 
<https://sourceware.org/glibc/wiki/MAINTAINERS>.  For subsequent port 
changes you'll need to say explicitly if you're looking for a review as 
otherwise people will assume you aren't, but people may still point out 
issues with port changes where you aren't looking for a review (being a 
subsystem maintainer is only a shortcut for assuming consensus for your 
changes to that subsystem, it does not guarantee there actually is 
consensus).

* Update <https://sourceware.org/glibc/wiki/ABIList> to list all the 
supported RISC-V ABIs (will need updating again in future if more 
supported ABIs are added).

* Update <https://sourceware.org/glibc/wiki/PortStatus> to reflect any 
features not handled for RISC-V (where there are list of architectures 
lacking some feature), specifically static PIEs unless you've tested that 
feature and determined it works.

* Update the <https://sourceware.org/glibc/wiki/Release/X.Y> template for 
release wiki pages to include slots for RISC-V results for each supported 
configuration.

* Add those slots to <https://sourceware.org/glibc/wiki/Release/2.27> as 
well, and fill them in with test results before the release is out on 1 
February.  This will need doing for each subsequent release during the 
one-month freeze period.

-- 
Joseph S. Myers
joseph@codesourcery.com