Release 5.13.1 - version bump and changelog for hotfix release

[jahnvi480]

Hotfix release 5.13.1 — version bump and changelog update.

Changes

• source/shared/version.h: SQLVERSION_PATCH 0 → 1, PECL strings → "5.13.1"
• CHANGELOG.md: Added 5.13.1 section with 5 bug fixes

Bug fixes included in 5.13.1 (already on release/5.13)

• An existing connection in the connection pool is reused unexpectedly even though it has a different access token. #1396 — Access token identity leaking across pooled connections (PR Fix | Access token identity leaking across pooled connections #1592)
• Prepared statement silently fails on insert - SET NOCOUNT ON fixes it #1588 — Prepared statement silently fails on insert (PR FIX: Prepared statement silently fails on insert - SET NOCOUNT ON fixes it #1590)
• Fatal error: Invalid column number in pdo_sqlsrv_stmt_get_col_data #1466 — Fatal error re-executing multi-resultset prepared statement (PR FIX: Freeing metadata entries and clearing the vector #1596)
• sqlsrv_connect does not try to establish a connection when there is no instance specified #1514 — sqlsrv_errors() returning null after connection failure (PR FIX: Silent failure during connection failure #1595)
• Binary stream returned from a statement becomes invalid if the statement gets implicitly closed #1443 — Binary stream invalid when statement goes out of scope (PR Fix stream invalidation when statement goes out of scope (GH#1443) #1598)

[David-Engel]

LGTM