Add GCC 14.1.0.

[guyutongxue]

Sorry for a so big PR, but it might be necessary to change these files.

Here is what it does:

• Add build scripts for gcc-14.1.0 and gcc-14-branch;
• Bump expat version (this suppresses #671 and fixes #672), because v2.5.0 no longer available to download due to vulnerability;
• Because GCC 14 starts to following ISO C standard strictly (and do not connivance "traditional" K&R C features like implicit function declaration etc.), some sub-targets failed when building with the newly-built GCC 14. That's why more changes are made:
• A test file modified.
• Upgrade gdb to 14.2. (Original version failed under GCC 14)
• Sub-target termcap and python-3 needs CFLAGS like -fpermissive or -Wno-error=implicit-function-declaration now.
• For python-3, an additional patch applied.
• For termcap, an additional patch applied (wtf the original Makefile do not use CFLAGS); AND ALSO, change the way to pass CFLAGS etc. to the configure script.
  • The original configure script doesn't recognize FOO=bar in command line arguments as environment variable (that's why in previous version, those CFLAGS settings are commented out).
  • I change the code to deal with PKG_CONFIGURE_FLAGS in func_configure, so that CFLAGS etc. are exported as environment variables instead of passing them as command line arguments.
  • In order to keep the PKG_CONFIGURE_FLAGS array structure as-is, now I'm using -n flag (a.k.a. pass array argument by reference) that supports from Bash 5.3 (ref, and ref). As a benefit, we can now remove all extra "escaped quotation mark" in *FLAGS settings.

I've tested these changes and successfully built GCC 14.1.0 with SEH, Win32, UCRT and v11 runtime. Let's wait for GitHub Actions' result.