libmpc: Update to version 1.3.1

libmpc: Update to version 1.3.1

- Update from version 1.2.1 to 1.3.1
- Update of rootfile
- Changelog
    Changes in version 1.3.1, released in December 2022:
	  - Bug fix: It is again possible to include mpc.h without including
	    stdio.h.
    Changes in version 1.3.0 ("Ipomoea batatas"), released in December 2022:
	  - New function: mpc_agm
	  - New rounding modes "away from zero", indicated by the letter "A" and
	    corresponding to MPFR_RNDA on the designated real or imaginary part.
	  - New experimental ball arithmetic.
	  - New experimental function: mpc_eta_fund
	  - Bug fixes:
	    - mpc_asin for asin(z) with small |Re(z)| and tiny |Im(z)|
	    - mpc_pow_fr: sign of zero part of result when the base has up to sign
	      the same real and imaginary part, and the exponent is an even
	      positive integer
	    - mpc_fma: the returned 'int' value was incorrect in some cases (indicating
	      whether the rounded real/imaginary parts were smaller/equal/greater
	      than the exact values), but the computed complex value was correct.
	  - Remove the unmaintained Makefile.vc; build files for Visual Studio
	    can be found at https://github.com/BrianGladman/mpc .

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Reviewed-by: Peter Müller <peter.mueller@ipfire.org>