scripts/functions: add a generic custom location infrastructure

Add a generic custom location infrastructure (inspired by the one in
kernel/linux) to allow the user to use custom tarballs or directories
for any component.

Signed-off-by: "David Holsgrove" <david.holsgrove@xilinx.com>
[yann.morin.1998@free.fr: move config option, improve help text, fix API doc]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <131c163c69f9cc81d2be.1349931191@localhost.localdomain>
PatchWork-Id: 190784
Message-Id: <0bbaba9190a76ba97f72.1349931192@localhost.localdomain>
PatchWork-Id: 190785

diff -durN glibc-2.12.1.orig/elf/dl-lookup.c glibc-2.12.1/elf/dl-lookup.c

--- glibc-2.12.1.orig/elf/dl-lookup.c	2009-03-30 23:14:32.000000000 +0200

+++ glibc-2.12.1/elf/dl-lookup.c	2009-11-13 00:51:36.000000000 +0100

@@ -301,6 +301,12 @@

 	      /* FALLTHROUGH */

 	    case STB_GLOBAL:

	    success:

+#ifdef __mips__

+	      /* HACK: MIPS marks its lazy evaluation stubs with SHN_UNDEF

+		 symbols, we skip them. */

+	      if (sym->st_shndx == SHN_UNDEF)

+		break;

+#endif

 	      /* Global definition.  Just what we need.  */

 	      result->s = sym;

 	      result->m = (struct link_map *) map;