pkg/libfixmath: add compile options to Kconfig

The option list has been taken from
https://code.google.com/archive/p/libfixmath/wikis/CompilationOptions.wiki.
The defaults are the current ones.

pkg/libfixmath/Kconfig

@@ -19,4 +19,64 @@ config MODULE_LIBFIXMATH_UNITTESTS
     depends on !HAS_ARCH_8BIT
     depends on !HAS_MSP430
 
+menu "Accuracy"
+
+config FIXMATH_NO_ROUNDING
+    bool "Disable rounding"
+    help
+        Say y to disable rounding. Results may round randomly up or down, i.e.
+        their accuracy is +-1. Runs slightly faster.
+
+config FIXMATH_NO_OVERFLOW
+    bool "Disable overflow detection"
+    help
+        Say y to disable overflow detection and saturating arithmetic support.
+        Overflowing computations will give garbage results. Runs slightly
+        faster.
+
+endmenu
+
+menu "Platform"
+
+config FIXMATH_NO_64BIT
+    bool "Disable use of uint64_t"
+    help
+        Say y to disable use of uint64_t in the code. Meant for compilers that
+        do not have 64-bit support. Runs the same speed or slightly slower.
+
+config FIXMATH_OPTIMIZE_8BIT
+    bool "Optimize for 8-bit architectures"
+    default y if HAS_ARCH_8BIT
+    help
+        Say y to use variants of the functions that are suitable for small 8- and
+        16-bit processors. Much faster on those processors, much slower on 32-bit
+        processors.
+
+config FIXMATH_NO_CACHE
+    bool "Do not use cache"
+    default y
+    help
+        Say y to avoid using cache for exp etc. function results. Uses less RAM,
+        runs slightly slower.
+
+endmenu
+
+menu "Algorithms"
+
+config FIXMATH_SIN_LUT
+    bool "Use sin look-up table generated by fixsingen"
+    help
+        Say y to use a look-up table generated by the fixsingen tool from svn,
+        it is faster on some devices but the lookup table takes up ~200KiB
+        (205376 bytes) in memory and can be slower depending on usage.
+
+config FIXMATH_FAST_SIN
+    bool "Fast sin approximation"
+    help
+        Say y to enable a faster but less accurate approximation of the sin
+        function, for code where accuracy isn't as important such as games logic
+        or graphics rendering then this is often a worthwhile tradeoff.
+
+endmenu
+
 endif # PACKAGE_LIBFIXMATH

pkg/libfixmath/Makefile.include

@@ -7,6 +7,10 @@ ifneq (,$(filter arch_8bit,$(FEATURES_USED)))
   CFLAGS += -DFIXMATH_OPTIMIZE_8BIT
 endif
 
+# translate Kconfig options to CFLAGS for the package
+libfixmath_options = $(filter CONFIG_FIXMATH_%,$(.VARIABLES))
+CFLAGS += $(libfixmath_options:CONFIG_FIXMATH_%=-DFIXMATH_%)
+
 INCLUDES += -I$(PKG_SOURCE_DIR)/libfixmath
 
 ifneq (,$(filter libfixmath-unittests,$(USEMODULE)))