* shlib-versions [USE_IN_LIBIO] (.*-.*-gnu-gnu*): Set earliest

* shlib-versions [USE_IN_LIBIO] (.*-.*-gnu-gnu*): Set earliest

	supported version for libc 0.2.90.libio to GLIBC_2.2.

	* Makeconfig (soversions.mk): Grok new third column in shlib-versions,
	and use it to emit new variable `map-firstversions'.
	* scripts/firstversions.awk: New file.
	* Makerules (Versions.all): Use scripts/firstversions.awk and
	the $(map-firstversions) value to generate a modified versions list
	that includes renames in "A = B" syntax for each version set earlier
	than the "earliest symbol version" named in shlib-versions.
	* scripts/versions.awk: Recognize "A = B" lines in the input to mean
	rename version set A to B in the output to the intermediate file.
	* scripts/abi-versions.awk: New file.
	* Makerules (abi-versions.h): New target, generated by that script.
	[$(versioning) = yes] (before-compile): Prepend abi-versions.h.
	* include/shlib-compat.h: New file, uses that generated header.