FTBFS with gcc 14

Description:

Package fails to build due to changes in gcc14. Adding #include <math.h> header fixes the build. https://gcc.gnu.org/gcc-14/porting_to.html

Additional info:

• package version: 0.5.0-6
• config and/or log files: Below
• link to upstream bug report, if any: N/A

Steps to reproduce:

1. Try to build
2. Fail

grader-tf.c: In function 'ots_calc_idf':
grader-tf.c:108:9: error: implicit declaration of function 'log' [-Wimplicit-function-declaration]
  108 | return -log(doc_word_count/term_count);
      |         ^~~
grader-tf.c:25:1: note: include '<math.h>' or provide a declaration of 'log'
   24 | #include "libots.h"
  +++ |+#include <math.h>
   25 | 
grader-tf.c:108:9: warning: incompatible implicit declaration of built-in function 'log' [-Wbuiltin-declaration-mismatch]
  108 | return -log(doc_word_count/term_count);
      |         ^~~
grader-tf.c:108:9: note: include '<math.h>' or provide a declaration of 'log'
make[2]: *** [Makefile:553: grader-tf.lo] Error 1
make[2]: Leaving directory '/build/libots/src/ots-0.5.0/src'
make[1]: *** [Makefile:495: all-recursive] Error 1
make[1]: Leaving directory '/build/libots/src/ots-0.5.0'
make: *** [Makefile:402: all] Error 2
==> ERROR: A failure occurred in build().
    Aborting...