i#1979 Mac64: 64-bit Mach-O drsyms support

Adds 64-bit Mach-O support to drsyms, which consists simply of looking for
LC_SEGMENT_64 in addition to LC_SEGMENT in drsyms_macho.c and in a
repatched version of libelftc.

Issue: #1979

ext/drsyms/drsyms_macho.c

@@ -203,7 +203,7 @@ find_load_base(byte *map_base, size_t *load_size)
     cmd = (struct load_command *)(hdr + 1);
     cmd_stop = (struct load_command *)((byte *)cmd + hdr->sizeofcmds);
     while (cmd < cmd_stop) {
-        if (cmd->cmd == LC_SEGMENT) {
+        if (cmd->cmd == LC_SEGMENT || cmd->cmd == LC_SEGMENT_64) {
             segment_command_t *seg = (segment_command_t *)cmd;
             if (!found_seg) {
                 found_seg = true;
@@ -371,7 +371,7 @@ drsym_obj_mod_init_pre(byte *map_base, size_t map_size)
     cmd = (struct load_command *)(hdr + 1);
     cmd_stop = (struct load_command *)((char *)cmd + hdr->sizeofcmds);
     while (cmd < cmd_stop) {
-        if (cmd->cmd == LC_SEGMENT) {
+        if (cmd->cmd == LC_SEGMENT || cmd->cmd == LC_SEGMENT_64) {
             segment_command_t *seg = (segment_command_t *)cmd;
             section_t *sec, *sec_stop;
             sec_stop = (section_t *)((char *)seg + seg->cmdsize);

ext/drsyms/libelftc-macho/libelftc-macho.patch

@@ -490,7 +490,7 @@ Index: libdwarf/libdwarf_macho_init.c
 +            cmd_stop = (struct load_command *)((char *)cmd + hdr->sizeofcmds);
 +        }
 +        while (cmd < cmd_stop) {
-+            if (cmd->cmd == LC_SEGMENT) {
++            if (cmd->cmd == LC_SEGMENT || cmd->cmd == LC_SEGMENT_64) {
 +                if (is_64) {
 +                    struct segment_command_64 *seg64 = (struct segment_command_64 *) cmd;
 +                    struct section_64 *sec64 = (struct section_64 *)(seg64 + 1);
@@ -547,7 +547,7 @@ Index: libdwarf/libdwarf_macho_init.c
 +        else
 +            cmd = (struct load_command *)(hdr + 1);
 +        while (cmd < cmd_stop) {
-+            if (cmd->cmd == LC_SEGMENT) {
++            if (cmd->cmd == LC_SEGMENT || cmd->cmd == LC_SEGMENT_64) {
 +                if (is_64) {
 +                    struct segment_command_64 *seg64 = (struct segment_command_64 *) cmd;
 +                    struct section_64 *sec64 = (struct section_64 *)(seg64 + 1);