Mine

--- toolchain/Config.in 2006-10-26 11:47:02.000000000 -0500
+++ toolchain/Config.in.new 2006-10-26 11:37:46.000000000 -0500
@@ -28,6 +28,13 @@
    help
        Enable large file (files > 2 GB) support

+config C99_MATH
+    bool
+    prompt "Enable full C99 math support?" if TOOLCHAINOPTS
+    default n
+    help
+        Enable if you need full C99 math in libm
+
 config SOFT_FLOAT
    bool
    prompt "Use software floating point by default" if TOOLCHAINOPTS
--- toolchain/uClibc/Makefile   2006-10-26 11:47:02.000000000 -0500
+++ toolchain/uClibc/Makefile.new   2006-10-26 11:41:45.000000000 -0500
@@ -52,6 +52,9 @@
 ifeq ($(CONFIG_SOFT_FLOAT),y)
    $(SED) 's,.*HAS_FPU.*,HAS_FPU=n\nUCLIBC_HAS_FLOATS=y\nUCLIBC_HAS_SOFT_FLOAT=y,g' $(PKG_BUILD_DIR)/.config
 endif
+ifeq ($(CONFIG_C99_MATH),y)
+   $(SED) 's,.*DO_C99_MATH.*,DO_C99_MATH=y,g' $(PKG_BUILD_DIR)/.config
+endif
    mkdir -p $(TOOLCHAIN_BUILD_DIR)/uClibc_dev/usr/include
    mkdir -p $(TOOLCHAIN_BUILD_DIR)/uClibc_dev/usr/lib
    mkdir -p $(TOOLCHAIN_BUILD_DIR)/uClibc_dev/lib