linux.c: don't use pread64

Starting with musl-1.2.4 all LFS64 APIs have been removed since musl is
always 64-bit and yara now fails with implicit function declarations for
pread64.

However configure.ac already sets AC_SYS_LARGEFILE so changing them all
to pread will work with both glibc and musl.

libyara/proc/linux.c

@@ -249,7 +249,7 @@ YR_API const uint8_t* yr_process_fetch_memory_block_data(YR_MEMORY_BLOCK* block)
   // target process VM.
   if (fd == -1)
   {
-    if (pread64(
+    if (pread(
             proc_info->mem_fd,
             (void*) context->buffer,
             block->size,
@@ -265,7 +265,7 @@ YR_API const uint8_t* yr_process_fetch_memory_block_data(YR_MEMORY_BLOCK* block)
     {
       goto _exit;
     }
-    if (pread64(
+    if (pread(
             proc_info->pagemap_fd,
             pagemap,
             sizeof(uint64_t) * block->size / page_size,
@@ -284,7 +284,7 @@ YR_API const uint8_t* yr_process_fetch_memory_block_data(YR_MEMORY_BLOCK* block)
       // swap-backed and if it differs from our mapping.
       uint8_t buffer[page_size];
 
-      if (pread64(
+      if (pread(
               proc_info->mem_fd,
               buffer,
               page_size,