Style fixes in pem, x509_crl and buf_alloc
diff --git a/library/memory_buffer_alloc.c b/library/memory_buffer_alloc.c
index 0d3342d..1cfc27c 100644
--- a/library/memory_buffer_alloc.c
+++ b/library/memory_buffer_alloc.c
@@ -184,7 +184,7 @@
 {
     memory_header *prv = heap.first, *cur;
 
-    if( heap.first == NULL || verify_header( heap.first ) != 0 )
+    if( prv == NULL || verify_header( prv ) != 0 )
     {
 #if defined(MBEDTLS_MEMORY_DEBUG)
         mbedtls_fprintf( stderr, "FATAL: verification of first header "