Follow-up of #408: Color class improvements

Better "#..." -> Color implem. (with from_chars), and some cleanup:
removing leftover junk (not just from Color).

+ Added -gdwarf-4 -gstrict-dwarf to the mingw build instead of -ggdb,
  as GDB didn't become more joy/less pain from the latter, but the DWARF
  data did enable debugging directly (no cv2pdb!) with WinDbg! :-o Yay!

tooling/build/Make-toolcfg.inc

@@ -60,8 +60,8 @@ CFLAGS_COMMON.msvc += ${CFLAGS_COMMON.msvc.$(LIB_MODE)}
 CFLAGS_COMMON.linux.debug_0 = -DNDEBUG
 CFLAGS_COMMON.linux.debug_1 = -DDEBUG -g -fsanitize=address
 CFLAGS_COMMON.mingw.debug_0 = -DNDEBUG -O3
-#!!CFLAGS_COMMON.mingw.debug_1 = -DDEBUG -O0 -g -ggdb #! Not with w64devkit: -fsanitize=address (See also at LDFLAGS!)
-CFLAGS_COMMON.mingw.debug_1    = -DDEBUG -O0 -g -ggdb -fsanitize=undefined -fsanitize-trap # w64devkit/issues/148
+#!!CFLAGS_COMMON.mingw.debug_1 = -DDEBUG -O0 -g #! Not with w64devkit: -fsanitize=address (See also at LDFLAGS!)
+CFLAGS_COMMON.mingw.debug_1    = -DDEBUG -O0 -g -gdwarf-4 -gstrict-dwarf -fsanitize=undefined -fsanitize-trap # w64devkit/issues/148
 CFLAGS_COMMON.msvc.debug_0 = -DNDEBUG
 CFLAGS_COMMON.msvc.debug_1 = -DDEBUG -Zi -fsanitize=address