Add predefined version identifiers for ELFv1 and ELFv2.

For PPC64 LittleEndian a new ELF version was defined. While the common usage is
ELFv1 with big endian and ELFv2 with little endian, the other uses are also possible.
In fact gcc defines a command line switch --with-abi=elfv1 / --with-abi=elfv2 to choose
the ELF ABI.
The new predefined version identifiers ELFv1 / ELFv2 reflect the fact that this
information cannot be determined elsewhere.
See http://llvm.org/devmtg/2014-04/PDFs/Talks/Euro-LLVM-2014-Weigand.pdf for more
information on ELFv2.

src/cond.c

@@ -213,6 +213,8 @@ bool VersionCondition::isPredefined(const char *ident)
         "Alpha_HardFloat",
         "LittleEndian",
         "BigEndian",
+        "ELFv1",
+        "ELFv2",
         "D_Coverage",
         "D_Ddoc",
         "D_InlineAsm_X86",

src/mars.c

@@ -444,25 +444,30 @@ int tryMain(size_t argc, const char *argv[])
 #elif TARGET_LINUX
     VersionCondition::addPredefinedGlobalIdent("Posix");
     VersionCondition::addPredefinedGlobalIdent("linux");
+    VersionCondition::addPredefinedGlobalIdent("ELFv1");
     global.params.isLinux = true;
 #elif TARGET_OSX
     VersionCondition::addPredefinedGlobalIdent("Posix");
     VersionCondition::addPredefinedGlobalIdent("OSX");
+    VersionCondition::addPredefinedGlobalIdent("ELFv1");
     global.params.isOSX = true;
 
     // For legacy compatibility
     VersionCondition::addPredefinedGlobalIdent("darwin");
 #elif TARGET_FREEBSD
     VersionCondition::addPredefinedGlobalIdent("Posix");
     VersionCondition::addPredefinedGlobalIdent("FreeBSD");
+    VersionCondition::addPredefinedGlobalIdent("ELFv1");
     global.params.isFreeBSD = true;
 #elif TARGET_OPENBSD
     VersionCondition::addPredefinedGlobalIdent("Posix");
     VersionCondition::addPredefinedGlobalIdent("OpenBSD");
+    VersionCondition::addPredefinedGlobalIdent("ELFv1");
     global.params.isFreeBSD = true;
 #elif TARGET_SOLARIS
     VersionCondition::addPredefinedGlobalIdent("Posix");
     VersionCondition::addPredefinedGlobalIdent("Solaris");
+    VersionCondition::addPredefinedGlobalIdent("ELFv1");
     global.params.isSolaris = true;
 #else
 #error "fix this"