Update to MPC version 1.2.0 with the following changes:

• New functions: . mpc_sum . mpc_dot
• Several functions are more robust with a reduced exponent range (for example corresponding to IEEE 754 binary formats).
• New mpcheck tool for comparison with the native C library (which is not installed by default).

Bump all directly dependent ports. Do not bump those indirectly
dependent via the lang/gcc* family since their run-time dependencies
and code generated should not be affected.

PR: 249950
Submitted by: wen