Description of problem:
The latest update of giac has made sagemath fail to build, with errors like this:

INFO: gcc: sage/libs/gsl/array.c
/usr/include/giac/plot.h:842:12: error: ‘uchar’ was not declared in this scope; did you mean ‘u_char’?
  842 | void blend(uchar r1,uchar g1,uchar b1,uchar r2,uchar g2,uchar b2,double t,uchar &r,uchar &g,uchar &b);
      |            ^~~~~
      |            u_char
/usr/include/giac/plot.h:842:21: error: ‘uchar’ was not declared in this scope; did you mean ‘u_char’?
  842 | void blend(uchar r1,uchar g1,uchar b1,uchar r2,uchar g2,uchar b2,double t,uchar &r,uchar &g,uchar &b);
      |                     ^~~~~
      |                     u_char
/usr/include/giac/plot.h:842:30: error: ‘uchar’ was not declared in this scope; did you mean ‘u_char’?
  842 | void blend(uchar r1,uchar g1,uchar b1,uchar r2,uchar g2,uchar b2,double t,uchar &r,uchar &g,uchar &b);
      |                              ^~~~~
      |                              u_char

I see a definition of uchar in signalprocessing.h, but there is no such definition in plot.h.

Version-Release number of selected component (if applicable):
giac-1.9.0.35-1.fc38.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Try to build sagemath in Rawhide
2.
3.

Actual results:
Errors due to a missing definition of uchar.

Expected results:
The headers should define the types they use.

Additional info: