Unbreak powerpc-unknown-linux-uclibc.

There is invalid assembly in dmalloc for PowerPC. The issue is that
'stw' expects a memory operand, and =g constraint allows both registers
and memory. Newer GCC tends to choose register even at -O0, resulting in
invalid assembly. Instead, force a register constraint in 'mflr' and let
GCC decide if it wants to store it into memory at all.

Reported this upstream.

Signed-off-by: Alexey Neyman <stilor@att.net>

patches/dmalloc/5.5.2/170-ppc-bogus-assembly.patch

@@ -0,0 +1,13 @@
+diff -ur dmalloc-5.5.2.orig/return.h dmalloc-5.5.2/return.h
+--- dmalloc-5.5.2.orig/return.h	2016-03-13 13:11:48.090431764 -0700
++++ dmalloc-5.5.2/return.h	2016-03-13 13:12:11.246642618 -0700
+@@ -251,8 +251,7 @@
+
+ #define GET_RET_ADDR(file) \
+ do { \
+-  asm("mflr 0"); \
+-  asm("stw 0,%0" : "=g" (file)); \
++  asm("mflr %0" : "=r"(file)); \
+ } while(0)
+
+ #endif /* __powerpc__ && __GNUC__ && !__OPTIMIZE__ */