Remove char/string conversions in fstab processing

There a few char->string conversions between functions which handle
different parts of fstab line processing, but there are no uses of
string functions. Pass char arrays/pointers around instead.

Change-Id: I976a9a54ee8dcfb6194cadcac6a34e467602003b
diff --git a/partitionmanager.cpp b/partitionmanager.cpp
index 95d2520..cc36b2e 100644
--- a/partitionmanager.cpp
+++ b/partitionmanager.cpp
@@ -90,11 +90,9 @@
 
 		if (fstab_line[strlen(fstab_line) - 1] != '\n')
 			fstab_line[strlen(fstab_line)] = '\n';
-		TWPartition* partition = new TWPartition();
-		string line = fstab_line;
-		memset(fstab_line, 0, sizeof(fstab_line));
 
-		if (partition->Process_Fstab_Line(line, Display_Error)) {
+		TWPartition* partition = new TWPartition();
+		if (partition->Process_Fstab_Line(fstab_line, Display_Error)) {
 			if (partition->Is_Storage) {
 				++storageid;
 				partition->MTP_Storage_ID = storageid;
@@ -113,6 +111,8 @@
 		} else {
 			delete partition;
 		}
+
+		memset(fstab_line, 0, sizeof(fstab_line));
 	}
 	fclose(fstabFile);
 	if (!datamedia && !settings_partition && Find_Partition_By_Path("/sdcard") == NULL && Find_Partition_By_Path("/internal_sd") == NULL && Find_Partition_By_Path("/internal_sdcard") == NULL && Find_Partition_By_Path("/emmc") == NULL) {