apply: Fix a patch corruption related to EOFNL handling

Use of apply's API can lead to an improper patch application and a corruption
of the modified file.

The issue is caused by mishandling of the end of file changes if there are
several hunks to apply. The new line character is added to a line from a wrong
hunk.

The solution is to modify apply_hunk() to add the newline character at the end
of a line from a right hunk.

src/apply.c

@@ -210,7 +210,7 @@ static int apply_hunk(
 			case GIT_DIFF_LINE_CONTEXT_EOFNL:
 			case GIT_DIFF_LINE_DEL_EOFNL:
 			case GIT_DIFF_LINE_ADD_EOFNL:
-				prev = i ? git_array_get(patch->lines, i - 1) : NULL;
+				prev = i ? git_array_get(patch->lines, linenum - 1) : NULL;
 				if (prev && prev->content[prev->content_len - 1] == '\n')
 					prev->content_len -= 1;
 				break;