Multiple font related optimization and improvements

[a740g]

Changes in this PR:

• The automatic fixed-width font detection feature is now disabled by default. Users can enable it by passing the "AUTOMONO" flag. Additionally, font flag changes are now correctly passed upstream to libqb.

• Font baseline calculation no longer relies on floating-point math. Instead, we utilize FreeType fixed-point functions such as FT_MulDiv() and FT_MulFix(). The baseline calculation method has also been refined for greater accuracy, ensuring precise baseline values.

• Significant enhancements have been made to the _U* functions. They now give more precise baseline-to-baseline height and font height measurements for both built-in and FreeType supported fonts. Superfluous adjustments that were previously applied have been eliminated, and all calculations now avoid floating-point math.

• Various quality-of-life enhancements have been implemented, including the usage of defined values instead of numeric literals and the use of std::string instead of qbs in func__loadfont().

[RhoSigma-QB64]

Works for me, tested my game with various fonts (fixed and proportional) and all looks as expected again.

[SteveMcNeill]

From what little testing I've did of these, they appear to be all working as advertised. Many thanks for keeping on these as much as you have. I appreciate it, and I know the vast majority of our user baser does too. :)