Restore ELF32_ST_INFO/ELF64_ST_INFO.

Mistakenly removed years ago, along with its genuinely duplicated companions.
This patch also redefines one of those rather than use the Linux uapi header
definition, which leads to signed/unsigned warnings in calling code.

Bug: https://github.com/android-ndk/ndk/issues/377
Test: ran tests
Change-Id: Ib25b17949f04969f12b945ca88ab87d080677cf9
diff --git a/libc/include/elf.h b/libc/include/elf.h
index c36bc8d..4181006 100644
--- a/libc/include/elf.h
+++ b/libc/include/elf.h
@@ -184,6 +184,12 @@
 
 #define PT_GNU_RELRO 0x6474e552
 
+#undef ELF_ST_TYPE
+#define ELF_ST_TYPE(x) ((x) & 0xf)
+#define ELF_ST_INFO(b,t) (((b) << 4) + ((t) & 0xf))
+#define ELF32_ST_INFO(b,t) ELF_ST_INFO(b,t)
+#define ELF64_ST_INFO(b,t) ELF_ST_INFO(b,t)
+
 #define STB_LOOS      10
 #define STB_HIOS      12
 #define STB_LOPROC    13