Fix (most) macOS compilation problems

src/runtime/c/Makefile.am

@@ -29,7 +29,7 @@ libpgf_la_SOURCES = \
 
 libpgf_la_LDFLAGS = -no-undefined
 libpgf_la_LIBADD = -lrt
-libpgf_la_CXXFLAGS = -fno-rtti
+libpgf_la_CXXFLAGS = -fno-rtti -std=c++11
 
 bin_PROGRAMS =
 

src/runtime/c/pgf/db.cxx

@@ -2,6 +2,8 @@
 #include <sys/mman.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <errno.h>
+#include <pthread.h>
 
 #include "data.h"
 
@@ -589,7 +591,7 @@ object PgfDB::malloc_internal(size_t bytes)
            invoked all that often in most programs. And the programs that
            it is called frequently in otherwise tend to fragment.
         */
-   
+
         idx = largebin_index(nb);
         if (ms->have_fastchunks)
             malloc_consolidate(ms);

src/runtime/c/pgf/db.h

@@ -112,6 +112,6 @@ private:
     DB_scope* next_scope;
 };
 
-extern PGF_INTERNAL_DECL thread_local DB_scope *last_db_scope __attribute__((tls_model("initial-exec")));
+extern PGF_INTERNAL_DECL __thread DB_scope *last_db_scope __attribute__((tls_model("initial-exec")));
 
 #endif