$(objpfx) directories, and get rid of vpath directives. The previous
arrangement resulted in files being written to the source directories
when run in a clean build. Find all .abilist files in $(..)abilist/.
(update-abi-%): Likewise.
(generated): Don't add .symlist files, they'll be intermediates.
* sysdeps/generic/init-first.c: Add a comment.
* elf/Makefile ($(objpfx)ld.so): Pass -z defs in link.
* scripts/gen-as-const.awk: Grok lone "--" as a separator between
#includes and expressions.
* scripts/merge-abilist.awk: Omit cpu-.*-os.*/modifier from merged
config list when it already contains cpu-.*-os.* without / part.
* Makerules (sed-remove-dotdot): New variable.
($(common-objpfx)%.make): Use it. Depend on $(before-compile).
($(common-objpfx)%.h $(common-objpfx)%.h.d): Likewise.
(check-abi-config): New variable, append /tls or /notls to the tuple.
(check-abi-%): Use that for -v config value.
Find .abilist files in abilist/libfoo.abilist, not in subdir.
* Rules: Move bits/stdio_lim.h generation rules to Makerules.
