Fix 2 functions calls with HIDDENSTRLEN

[jamesjer]

The Fedora project is in the process of rebuilding all packages with GCC 15, which defaults to the C23 standard. One major change in C23 is that declarations of the form type f(); no longer mean "a function that returns type with an unspecified parameter list". Now such a declaration means "a function that returns type with an empty parameter list"; i.e., it is the same as type f(void);. This has caused quite a few packages to fail to build, including the Csdp package. While working with the sources to resolve this issue, one thing I did was to replace the BLAS and LAPACK function declarations at the bottom of include/declarations.h with the appropriate #include directives. This turned up two cases where function calls failed to match the declarations. We use a library where HIDDENSTRLEN needs to be defined (flexiblas). This PR fixes both cases.

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