ld.so: Do not export free/calloc/malloc/realloc functions [BZ #25486]

Exporting functions and relying on symbol interposition from libc.so
makes the choice of implementation dependent on DT_NEEDED order, which
is not what some compiler drivers expect.

This commit replaces one magic mechanism (symbol interposition) with
another one (preprocessor-/compiler-based redirection).  This makes
the hand-over from the minimal malloc to the full malloc more
explicit.

Removing the ABI symbols is backwards-compatible because libc.so is
always in scope, and the dynamic loader will find the malloc-related
symbols there since commit f0b2132b35
("ld.so: Support moving versioned symbols between sonames
[BZ #24741]").

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

sysdeps/unix/sysv/linux/sh/be/ld.abilist

@@ -1,9 +1,5 @@
 GLIBC_2.2 __libc_stack_end D 0x4
 GLIBC_2.2 _dl_mcount F
 GLIBC_2.2 _r_debug D 0x14
-GLIBC_2.2 calloc F
-GLIBC_2.2 free F
-GLIBC_2.2 malloc F
-GLIBC_2.2 realloc F
 GLIBC_2.3 __tls_get_addr F
 GLIBC_2.4 __stack_chk_guard D 0x4

sysdeps/unix/sysv/linux/sh/le/ld.abilist

@@ -1,9 +1,5 @@
 GLIBC_2.2 __libc_stack_end D 0x4
 GLIBC_2.2 _dl_mcount F
 GLIBC_2.2 _r_debug D 0x14
-GLIBC_2.2 calloc F
-GLIBC_2.2 free F
-GLIBC_2.2 malloc F
-GLIBC_2.2 realloc F
 GLIBC_2.3 __tls_get_addr F
 GLIBC_2.4 __stack_chk_guard D 0x4

sysdeps/unix/sysv/linux/sh/localplt.data

@@ -12,12 +12,6 @@ libc.so: __errno_location
 libm.so: matherr
 # Generated by the compiler because there is no trap insn pattern.
 libc.so: abort ?
-# The main malloc is interposed into the dynamic linker, for
-# allocations after the initial link (when dlopen is used).
-ld.so: malloc
-ld.so: calloc
-ld.so: realloc
-ld.so: free
 # The TLS-enabled version of these functions is interposed from libc.so.
 ld.so: _dl_signal_error
 ld.so: _dl_catch_error